Answer:
n = d+30 since he has 30 more nickels than dimes, to make them equal you have to add 30 to the dimes.
:
n+d = 150 substitute for n:
d+30+d = 150
2d = 120
d = 60 he has 60 dimes and 150-60 = 90 nickels
40 I hope I helped you
