#!/bin/bash

echo 'Using $(()) arithmetic expansion'
echo "$1 + $2 = $(($1 + $2))"
echo

echo "Using simple variable"
SUM="$1 + $2"
echo "$1 + $2 = $SUM"
echo

echo "Declaring variable with let"
let LET_SUM="$1 + $2"
echo "$1 + $2 = $LET_SUM"