Question 387709
Let N= number of Nickels, each worth 5 cents
Let D= number of Dimes, each worth 10 cents


5N + 10D = 210
5(N+24)+ 10(3D) = 630


5N + 10D = 210
5N+120 + 30D=630
 

In the second equation, subtract 120 from each side:
5N + 10D = 210
5N + 30D = 510


Multiply both sides of first equation by -1 to eliminate the N variables:
-5N - 10D = -210
5N  + 30D =  510


Add the two equations together:
20D = 300


Divide both sides by 20
D=300/20=15 Dimes


5N + 10D = 210
5N + 10*15= 210
5N + 150 = 210
5N = 60
N= 12 Nickels


Check:
5(N+24) + 10(3D) = 630
5(36) + 10(45) = 630
180 + 450 = 630


IT CHECKS!!


Dr. Robert J. Rapalje, Retired