Algebra problem

Question

3 dollars made in nickels dimes and quarters twice as many dimes as quarters and five more nickels than dimes. how many coins does he have of each? 

Answer 1

Let n represent nickels, d dimes and q quarters. We know the total value is 3 dollars or 300 cents. Therefore:

 

300 = 5n + 10d +25q

 

Furthermore, we know q = d/2 and n = d + 5. Making those substitutions:

 

300 = 5(d+5) + 10d + 25(d/2)

300 = 5d + 25 + 10d + 12.5d

275 = 27.5d

10 = d

q = 10/2 = 5

n = 10 + 5 = 15