There's 4 quarters to every dollar so if you have 80 quarters you would have $20.00
4x 10 would equal 40 so if you had 40 quarters you'd have $10.00 but if you take 4 x 20 you would have 80 quarters so 4 x 20 is 80 quarters which equals $20.00
Another way to add this equation up is to take $0.25 x 80 which would equal $20.00
So in short you have $20.00 if you have 80 quarters.