## Elementary Algebra

The interest formula is: interest due = principal $\times$ yearly rate of return $\times$ time in years. This formula can be written as i = P $\times$ r $\times$ t. P = 10,500 r = 5% = 0.05 t = 4 Substitute these values into the equation to obtain: i = 10500 $\times$ 0.05 $\times$ 4 i = 42000 $\times$ 0.05 i = 2100 2100 dollars is due on the student loan.