10d + 25q + 50h = 2000

d + q + h = 110

d = 6h - 2

So we have this system of equations:

10d + 25q + 50h = 2000
d + q + h = 110
d = 6h - 2

Arrange them like this:

10d + 25q + 50h = 2000
  d +   q +   h =  110
  d       -  6h =   -2

Can you solve that system? If not post again asking how.

Solution:

d = 70, q = 28 and h = 12

So there are 70 dimes, 28 quarters and 12 half dollars.

Checking:

 70 dimes makes         $7
 28 quarters makes      $7
 12 half dollars makes  $6
--------------------------
110 coins makes        $20

Six times the number of half dollars = 6×12 = 72
2 less than 72 is 70 and that is the number of dimes.

Edwin