A bag contains 28 blue and green tiles. The bag contains two blue tiles for every 5 green tiles. Which proportion can be used to find y, the total number of green tiles in the bag?

8 blue tiles and 20 green tiles in the bag

Explanation:

Let b represent the number of blue tiles and g the number of green tiles. Since bag contains 28 blue and green tiles hence:

b + g = 28            (1)

Also, there is two blue tiles for every 5 green tiles, hence:

2g = 5(b);

5b - 2g = 0           (2)

Multiply equation 1 by 5 and subtract equation 2 from the result:

7g = 140

g = 20

b + g = 28; b + 20 = 28

b  = 8

Therefore there are 8 blue tiles and 20 green tiles in the bag