I think this is what your equation is, let me know if I am reading it incorrectly:
First, think of 40 as the same thing as . When you multiply fractions, you just multiply the bottoms by each other and the tops by each other. So this would give you:
Then multiply both sides by 35 to get rid of your fraction. This will leave you with 40x = 19,600. Then divide both sides by 40 and that will give you your answer!