gary has 100 quarters and dimes. If the total value of the coins is $15.70, how many quarters and dimes do you have?
q(.25) + (100-q)(.1) = 15.70
.25 q + 10 - .1 q = 15.7
.15 q = 5.7
q = 38
then dimes = 100 - 38 = 62
check
38(.25) + 62(.1) = 15.7 yes