Rick has a box of coins .The box currently contains 51 coins, consisting of pennies, dimes and quarters. The numbers of pennies is equal to the numbers of dimes and the total value is $5.73. How many of each denominations of coins does he have?

the number of pennies which is equal to the number of dimes is?
the number of quarters is?

1 answer

p = d

p + d + q = 51

p + 10 d + 25 q = 573 cents
so

2 p + q = 51
11 p + 25 q = 573

multiply the first equation by 25 and subtract

50 p + 25 q = 1275
11 p + 25 q = 573
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39 p = 702
p = 18 etc