What is the answer for this problem

In the figure shown below, m < 40 and ab =8. which equation could be used to find x?

Ricky takes out a $31,800 student loan to pay his expenses while he is in college. after graduation, he will begin making payments of $190.66 per month for the next 30 years to pay off the loan. how much more will ricky end up paying for the loan than the original value of $31,800? ricky will end up paying $ more than he borrowed to pay off the loan.

Another type of subtraction equation is 16-b=7. explain how you would sole this equation then solve it.