pietro borrows 14000 some is from his friend at 2 annual int

pietro borrows $14,000. some is from his friend at 2% annual interest, three times as much as that from his bank at 7%, and the remining from his insurance company at 11%. He pays a total of $1,260 in interest for the first year. how much should he borrow from the bank?

Solution

Let he borrowed 3A, A and B amounts from his friend, his bank and from his insurance company.

4A+B = 14000

and also 0.02*3A + 0.7*A + 0.11*B = 1260 this means 76A + 11B = 12600

from these two equations we get B = $ 31,675