70% of stamps are Canadian, rest are international, 500 more Canadian stamps, how many’ stamps all together?

Question

In Tina's stamp collection, 70% of the stamps are Canadian and the rest are international. Tina has 500 more Canadian stamps that international stamps. How many stamps does she have?

Answer 1

If n=total number of stamps then 0.7n are Canadian and 0.3n are international.

The difference between these quantities is 500 so 0.7n-0.3n=500. Therefore 0.4n=500, n=500/0.4=1250 stamps altogether (875 Canadian and 375 international).