Final answer:
Diego has 7 nickels and 21 quarters.
Step-by-step explanation:
Let's say the number of nickels Diego has is 'x'. Since he has 3 times as many quarters as nickels, the number of quarters he has will be 3x.
The value of a nickel is 5 cents and the value of a quarter is 25 cents. So, the total value of the nickels will be 5x cents and the total value of the quarters will be 25(3x) = 75x cents.
We are given that the combined value of all the coins is 560 cents. Therefore, we can set up the equation 5x + 75x = 560 to find the value of 'x'.
Simplifying the equation, we get 80x = 560.
Dividing both sides by 80, we find that x = 7.
Since 'x' represents the number of nickels, Diego has 7 nickels. And since he has 3 times as many quarters, he has 3(7) = 21 quarters.
Therefore, the correct answer is option D) 11 quarters, 5 nickels.