The fraction on the right is 35% over 100%. the 35% represents the percentage the 6th graders raised of the total money raised.
The fraction on the left is x (representing how many dollars the 6th graders raised, what we're trying to find) over $240, the total amount raised by the school.
1. cross multiply 35 with 240. 35x240=8400 2. Since we are looking for x and 100 is across from it you divide what you got from the first multiplication by 100 8400/100=(100*x)/100 =$84