What you have to do is find what 1/3 is of 120 and 1/4 of 120.
120/3=40, so each third is 40 bricks
120/4=30, so each fourth is 30 bricks
Add those together
The total of the red bricks and blue bricks is 70
120-70= 50
There would be: 40 red bricks, 30 blue bricks, and 50 green bricks