How to write shell script that will add two nos, which are supplied as command line argument, and if this two nos are not given show error

if [ $# -ne 2 ]
then
echo “Usage – $0 x y”
echo ” Where x and y are two nos for which I will print sum”
exit 1
fi
echo “Sum of $1 and $2 is `expr $1 + $2`”