You have to find two numbers, but there is a relation between them. In algebra like this, we try to reduce the problem to just one unknown number.
Let L = larger number and S = smaller number
L + S = 35
4L = 5S - 4
If you re-write these, solving for L each time, you get
L = 35 - S
L = (5S - 4 ) / 4
These are the same S and L we're talking about, so that means that
35 - S = (5S - 4) / 4
Now you just have to solve for S and then use that value in the equation L = 35 - S to get the other number.
Hope this helps!
Stephen La Rocque>