Jessica has 9 more nickels than dimes, and the total value of her coins is 1.50. How many nickels does she have. Write the best equation.

d = n-9

5 n + 10 d = 150 cents

5 n + 10(n-9) = 150

15 n -90 = 150

15 n = 240

n = 16

To write the best equation to solve this problem, we need to define some variables.

Let's say:
N = the number of nickels
D = the number of dimes

According to the problem, Jessica has 9 more nickels than dimes. This can be expressed as:
N = D + 9

We also know that the total value of her coins is $1.50. The value of a nickel is $0.05, and the value of a dime is $0.10. So, we can write the equation for the total value of her coins as:
0.05N + 0.10D = 1.50

Therefore, the best equation to represent the problem is:
N = D + 9
0.05N + 0.10D = 1.50