Shell Programming and Scripting

What i need to change in this statment?
exp1=$sum*100/$failed
echo the failed percentage is 1 expr $exp1 | bc `

u mean to say the decalration of this sum,failed,passed should be shared with " ` " this symbol?

lready using a script which stores
values in variable like sum, passed, and failed.
add these lines
exp1=$sum*100/$failed
echo the failed percentage is ` expr $exp1 | bc `
similarly do for pass percentage
and be carefule, the characters are not single quotes but the one above tab key.
expr $exp1 | bc should be enclosed between ``
expr is for calculation of expression passed to bc
and the result is echoed on screen.