Bob has 4 more dimes than nickels. He has 1.45 in all. How many nickels does he have? Please explain and show your work.
Let N be the number of nickels. Let D be the number of dimes.
D - N = 4
10D + 5N = 145 (the number of cents)
Substitute N + 4 for D in the second equation and solve for N.
10N + 40 +5N = 15N + 40 = 145
15N = 105
Take it from there.