This could be calculated using the proportion. If the value of the car decreases by 15% each year, that means that after each year the value of the car is 85% of the value from the first year.
Number of pennies:P Number of nickels:N Number of dollar bills:D P=N+12 N=D+5 1P+5N+100D=996 ^given Therefore P=(D+5)+12 P=D+17 Plug back into main equation (D+17)+5(D+5)+100D=996 Combine like terms 106D+42=996 106D=954 D=954/106=9