Answer:
$7.00
Explanation:
If you do an equation, you'll have 
 where
 where 
 =money per hour and
=money per hour and 
 =total money
=total money
The total amount of money will be what he had left, plus the money spent on the cake
If he expends $12 and still has $86 left the total will be 

Now you know the total and the number of hours worked on the week so, you need to resolve 
 and you'll find
 and you'll find 
 =$7.00
=$7.00