You want to first find the connection between the first statement, y=10 and x=20. The connection is that Y is X divided by 2. Then you want to just do the same equation to the y and keep it a fraction. (Hint. a fraction is the same as what you do to divide, its just the equation before you find your answer.) so your answer is 15/2.
Even though we are using variables, we still know that "difference" means subtraction. So, if the larger is x1 and x2, those variables go first. The smaller, y1 and y2 will go second. So our problem will look like this:
