An artist is making a mosaic using glass tiles. He uses a total of 600 tiles.
The ratio of red tiles to blue tiles is 1:2.
How many red tiles does he use?

200

Step-by-step explanation:

Let x and 2x be the number of red tiles and blue tiles respectively.

x + 2x = 600

3x = 600

=> x = 200

No. of red tiles = 200

No. of blue tiles = 2(200) = 400

so, converting firstly the mixed fractions to improper fractions and then "adding".