Answer:
$40
Explanation:
The use of the word "mental math" means round to the nearest whole. By doing this you turn $12.98 into $13 and $1.02 into $1 which will give you $40 in total. This problem doesn't need to round as it is a simple problem. The true answer is $12.98 + $17.50 + $8.50 +$1.02= $40.