Answer:
There are 25 nickels, 20 dimes and 40 quarters
Explanation:
Let
x ----> the number of nickels coins
y ----> the number of dimes coins
z ---> the number of quarters coins
Remember that

we know that
----> equation A
----> equation B
----> equation C
Substitute equation C in equation A and equation B

-----> equation D

-----> equation E
Solve the system of equations D and E by graphing
Remember that the solution of the system is the intersection point both graphs
The solution is the point (25,20)
see the attached figure
Find the value of z

therefore
There are 25 nickels, 20 dimes and 40 quarters