Here is our problem
Draw 3/7, make sure the lines are going the other way.
Draw 3/7 the same way you did in the smaller picture, but bigger.
Draw 2/5 on top.
Find out how many boxes have both colors drawn in it.
The numbers of boxes is your numerator.
To find the denominator count how many total boxes there are. Than simplify if needed.
This is our answer.
- Any color marker