adding value to variable using expr

for i `cat abc.txt`
do
m= `expr $i + 2`
echo $m
done
i wrote this script to assing value to m. but i got the error

"a.sh[6]: 423: not found"

please help me to sort out this issue

Remove the space after the equal sign (=) in this statement:

m= `expr $i + 2`

worked thanks