SOLUTION: Peter has been saving his loose change for several days. When he counted his quarters and dimes, he found they had a total value of $13.10. The number of quarters was 15 more than

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Question 1137304: Peter has been saving his loose change for several days. When he counted his quarters and dimes, he found they had a total value of $13.10. The number of quarters was 15 more than 3 times the number of dimes. How many quarters and how many dimes did Peter have?
Answer by math_helper(2461) About Me  (Show Source):
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Let:
d = number of dimes
q = number of quarters



Based on the value of the coins, one can write this equation:

10d + 25q = 1310  (1)   (in cents)



Another equation can be written based on the information given that relates number of quarters to number of dimes:

q = 15 + 3d       (2)



One way to solve is to substitute 'q' in (1) the RHS of (2), then solve for the single unknown 'd'.  Finally, use (plug in) that value of 'd' into (2)  (or (1), but (2) looks easier) and solve for q.   Don't forget to check your answer.