Interest

That depends on how much you borrow
on the interest rate
on how big the repayments are and how often they are made
and very importantly on whether it is simple interest or compound interest.
If it is compound interest you would need to know how often it is componding as well.

Simple interest questions are usually faily easy
Compound interest questions are much harder.

If you borrow a little amount you might pay simple interest but if you borrow a big amount like for a house, it will always be compound (or reducible) interest.