So her prescriptions cost $37.13 and she paid $50. You’re finding how much change Janet will get back. All you have to do here is to take the amount of money she used to pay and subtract it with the amount she needs to pay.
So $50 (or $50.00 since some people understand it better when there are the same amount of digits) minus $37.13.
$50.00
-$37.13
—————
$12.87
Janet got $12.87 back.
