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    "# Expressions\n",
    "\n",
    "**Expressions** are the base unit in Python (and indeed, in most programming languages). You can think of these as similar to \"terms\" in a typical algebraic equation, though we'll see shortly how that analogy doesn't go very far.\n",
    "\n",
    "Python always tries to calculate **expressions** to the most literal value possible. Consider putting `2 + 4` into a calculator. In this example, we don't really care about the equation `2 + 4`, but rather _the result_. Likewise, Python cares about the result, and tries to do whatever work is required to get there -- in this case, addition.\n",
    "\n",
    "Expressions are usually composed of other expressions; this allows us to create equations and formulas more interesting than just the two-term `2 + 4`. In fact, we even consider the numbers themsevles expressions: `2` and `4` are each expressions which are composed together with the `+` operation to form the full expression."
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    "2"
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   "execution_count": 3,
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       "4"
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    "4"
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   "cell_type": "code",
   "execution_count": 4,
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    {
     "data": {
      "text/plain": [
       "6"
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     "execution_count": 4,
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   "source": [
    "2 + 4"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python follows all of the expected order of operations in mathematics (\"PEMDAS\"), and evaluates inside-out, left-to-right. As such, the following two expressions result in different evaluations:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
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     "data": {
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       "42"
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     "execution_count": 5,
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   "source": [
    "3 * 4 + 5 * 6"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
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    {
     "data": {
      "text/plain": [
       "162"
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     "execution_count": 6,
     "metadata": {},
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   ],
   "source": [
    "3 * (4 + 5) * 6"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Given the following, how many expressions are there?"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "22.22222222222222"
      ]
     },
     "execution_count": 7,
     "metadata": {},
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    }
   ],
   "source": [
    "(72 - 32) / 9 * 5"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "(72 - 32) / (9 * 5)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "(72 - 32)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "72 - 32"
   ]
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   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "32"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
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   ],
   "source": [
    "32"
   ]
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  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "72"
      ]
     },
     "execution_count": 9,
     "metadata": {},
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   "source": [
    "72"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "40 / 45"
   ]
  }
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