The graph of y=f(x) is graphed. given that f is invertible, find f^-1(4)​

Could answer every question with steps

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.

2x minus y equals 6, x plus y equals negative 3