Answer:
N=250
Explanation:
"twice as many nickels as dimes" means N =2D [eq1]
"collection of nickels and dimes is worth $25" means
5N + 10D = 2500 [eq2]
(To avoid using decimal points, PLZ express everything in cents.)
Substitution (substitute N from eq1 into eq2]:
5(2D) + 10D = 2500
10D + 10D = 2500
20D = 2500
D = 125
N=2D [eq1 again]
N=2(125)
N=250
Check:
Is 5(250) + 10(125) = 2500 ?
1250 + 1250 = 2500 ?
2500 = 2500 ?yes