Lucy has $1.35 in nickels and dimes in her pocket. If she has six more dimes than nickels, which equation can be used to determine x, the number of nickels she has?
d = x + 6
10 d + 5 x = 135
10 (x+6) + 5 x = 135
15 x + 60 = 135
15 x = 75
x = 5 nickels