#!/bin/bash
# Basic arithmetic using double parentheses
a=$(( 4 + 5 ))
echo $a # 9
a=$((3+5))
echo $a # 8
b=$(( a + 3 ))
echo $b # 11
b=$(( $a + 4 ))
echo $b # 12
(( b++ ))
echo $b # 13
(( b += 3 ))
echo $b # 16
a=$(( 4 * 5 ))
echo $a # 20
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