This math problem has got me stumped: Jack and Jill are friends who borrow from each other often. Last week Jack borrowed  $1200 from Jill, which he promised to pay back with an interest of 10%. How much will Jack pay back?
Can you show me the way?
The interest on the loan is 0.1*1200=$120
The total amount Jack needs to pay back is 1200+120=1320