Ed had w more marbles than Doug. Doug lost x of his marbles at the playground. If Ed had y marbles How many marbles does Doug have now?
First, we need to find out how many marbles Doug had in the beginning. We know that Ed had w more marbles than Doug, and we know that Doug lost x of his marbles at the playground. This means that Doug must have had w - x marbles in the beginning. 

Now, we need to find out how many marbles Doug has now. We know that Ed has y marbles, and we know that Doug has w - x marbles. This means that Doug must have y - (w - x) marbles now. 

Therefore, the answer (symbolic expression) is: 

y - (w - x)