For this case, the first thing we must do is define variables: x = number of quarters y = number of dimes We now write the system of equations: x + y = 28 0.25x + 0.10y = 4.05 Solving the system of equations we have: x = 8.33 y = 19.66 Rounding: x = 8 y = 20 Answer: the college student has: 8 quarters 20 dimes