Question 998159
p = number of pennies
n = number of nickels
q = number of quarters


p + 5n + 25q = 127
q = 2p
p + n + q = 11


Substitute q = 2p into the first and third equations.


p + 5n + 25(2p) = 127 ---> 51p + 5n = 127 (eqn 1)
p + n + 2p = 11 ---> 3p + n = 11 (eqn 2)


Multiply the second equation by 5.


51p + 5n = 127
-(15p + 5n = 55)
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36p = 72 ----> p = 2


Collin has 2 pennies, 5 nickels, and 4 quarters.