Posted by Kevin on .
A bag holds 57 green and blue marbles. There are 13 more blue marbles then green marbles. How many marbles of each color are there?

Math 
abc,
x=green marbles
y=blue marbles
x+y=57
x+13=y b/c there are 13 more blue marbles
substitute in to other equation
x+(x+13)=57
then solve for x, then for y add 13 to x