arithmetic operation

echo Arithmetic operation
num1=10
num2=15

echo one way
echo $num+$num2
echo $num1*$num2
echo $num1/$num2
echo $num1-$num2

echo another way
echo $((num1*num2))
echo $((num1+num2))
echo $((num1-num2))
echo $((num1/num2))

echo another way
echo $(expr $num1 + $num2 )
echo $(expr $num1 - $num2 )
echo $(expr $num1 * $num2 )
echo $(expr $num1 / $num2 )