Question

15h/5h+10h/5h+25/5h=x+y+5/h

Answer 1

First simplify:
15h/5h becomes 3 (because 15h & 5h are divisible by 5h)
     3+10h/5h+25/5h=x+y+5/h
10h/5h becomes 2 (because 10h & 5h are divisible by 5h)
     3+2+25/5h=x+y+5/h
25/5h becomes 5/h (because 25 & 5 are divisible by 5)
     3+2+5/h=x+y+5/h
Add 3+2=5
     5+5/h=x+y+5/h
subtract -5/h from both sides, which cancel's each one out.
     5=x+y
Now depending on whether you are solving for x or y, subtract the opposite, leaving the one you are solving for left by itself, as the one you subtract will cancel itself out on the right side.
5-y=x  or x=5-y
or 
5-x=y or y=5-x