Jenn has 13 fewer marbles then Marty. she has 20 marbles. which equation can be solved to find how many marbles Marty has?

If jenn has 13 fewer marbles than marty and we know she has 20 marbles, you would add 13 to 20 (33) to find how many marbles marty has. the equation would be 13+20=33 (or any variable depending on the context of the question.)