Substraction in bash

UNIX Solaris
1

Hi all,

I have in one script something like this:

FIRSTOCC=`grep -n ORA- alert_bill2.log |tail -"$ROWS"|head -1|cut -d: -f1`
TOTAL=`more alert*|wc -l`

DIFFERENCE=`$TOTAL-$FIRSTOCC`

echo Total lines in alert_bill = $TOTAL
echo $DIFFERENCE

How do I make this substraction work?
Thk

2 
DIFFERENCE=$((TOTAL-FIRSTOCC))

echo $DIFFERENCE
3

Thank you very much ! :wink:
Was fast too...