Question

Michelle collects US, Canadian and Mexican stamps. In her collection 80% of the stamps are U.S. and Mexican stamps. there are 3 times as many U.S. stamps as Mexican stamps. WHat percent of Michelle's collections is made up of U.S. stamps?

Answer 1

We know that 80% of the stamps are US and Mexican. 
The US stamps are 3 times the Mexican stamps. That means that of the 80%, Mexicans comprised of the 20% and US comprised of the 60% to satisfy the relationship of their ratios. 

Therefore, 60% of Michelle's collection is made up of US stamps.