This is a great problem to set up a proportion. We know that 480 people is 75% of some population, let's call it P. So we know that 480/P = 75/100 (because 75/100 is 75%). Therefore, we would solve 480/P=75/100, which would yield, 480*100=75P (cross multiplication). Then P=(480*100)/75. P=640.
