Ed had 1 more marbles than Doug. Doug lost some of his marbles at the playground. Now Ed has 11 more marbles than doug. How many marbles did Doug lose?
1. Ed had 1 more marbles than Doug. 
2. Doug lost some of his marbles at the playground. 
3. Now Ed has 11 more marbles than Doug.

We can see that Doug lost 10 marbles at the playground.