Can someone help me figure this out

Let x be the number of nickels. We know that the number of dimes is 5 less than twice the number of nickels, so the number of dimes is 2x−5. We also know that Kaitlen has $2.25 in nickels and dimes. This means that 0.05x+0.10(2x−5)=2.25. Solving for x, we get x=9. Therefore, Kaitlen has 9​ nickels.

D=2*N  - 5,     

5N + 10D ==225, solve for D, N

Use substitution to get:

D==17 - number of dimes

N==11 - number of nickels.