This is about adding and subtracting expressions with the same denominators. Go back to simple arithmetic such as 5/6-2/6. All you do is go right across and 1.)Add or subtract the numerator (5-2). 2.) Keep the denominator. 3.) Change to lowest terms. Use the same general rules. In the problem: 9f+6g/6 - 6g-9f/6, you put the numerator all together so that it reads: 9f +6g - (6g-9f) put parenthesis around the second part so you don't forget to distribute the whole part. The 6g's cancel out and you get 9f plus 9f which is 18f/6 which equals 3f. Another problem: y^2/(y+5) + 5y/(y+5). It goes down to y^2+5y/(y+5). Combine to lowest terms. The (y+5)'s cancel out and you get the answer as y.