Devin borrowed $1,058 at 13 percent for nine months. what will he pay in interest? how much is his total payment? what will be his monthly payment?

Given:
amount borrowed: 1,058
interest rate: 13%
term: 9 months

I'm assuming that the 13% rate is the annual interest rate. I'm also assuming that this problem is a simple interest problem.

Interest = Principal * rate * term
Interest = 1,058 * 13% * 9/12
Interest = 103.16

Total payment = Principal + interest
Total payment = 1,058 + 103.16 = 1,161.16

His monthly payment will be:
1,161.16 / 9 mos = 129.02

Devin will pay a 129.02 per month for 9 months to pay off his loan principal of 1,058 and the interest of 103.16.