Answer:
First, denote the number of dimes as x, and the number of quarters as y.
Since the total number of coins equals 61, we can write the following equation: x + y = 61
Since the total value of the coins equals $10.90, and we know that a quarter is worth $0.25 and a dime is worth $0.10, the total value can be expressed as a function of the number of quarters and dimes: $0.10*x + $0.25*y = $10.90
Now, we have two equations and two variables, meaning we can solve the 2x2 system!
Rewrite the first equation in terms of x: x = 61 - y
Now substitute this expression into the second equation: $0.10*(61-y) + $0.25*y = $10.90
Solve for y: $.15*y = $4.80, y = 32
Substitute back into the first equation to get x: x = 29
She indeed has 3 more quarters than dimes since 32-29= 3, so we did it right (:
Explanation: