Ed had 42 more marbles than Doug. Doug lost 44 of his marbles at the playground while Ed found 9 more marbles. How many more marbles did Ed have than Doug then?
Ed had 42 more marbles than Doug to start with. 
Doug lost 44 marbles, which means he now has -2 marbles. 
Ed found 9 more marbles, which means he now has 51 marbles. 

So, Ed has 51 marbles and Doug has -2 marbles. Therefore, Ed has 53 more marbles than Doug.