#### Answer

10 quarters, 8 dimes, and 2 nickels.

#### Work Step by Step

We are told:
$ d + q + n = 20$
And
$ .1d + .25q + .05n = 3.4$
And
$ d + n = q$
Substituting q for d + n in equation one, we obtain:
$ 2q = 20 \\ q = 10$
Thus, we are left with:
$ .1d + .05n = .9$
And
$ d + n = 10$
Using d = 10 - n, we find:
$.1(10 - n) + .05n = .9 \\ -.05n = -.1 \\ n = 2$
This means that the number of dimes is:
$ d = 10 -2 = 8$