Little Tommy built a train out of blocks. One-third of the train was made with blue blocks, 2/5 of the train was made with red blocks and the remaining eight blocks were yellow.

1/3+2/5 = 5/15 + 6/15 = 11/15.

1-11/15 = 15/15-11/15 = 4/15 = yellow blocks.

4x/15 = 8
X = 30 Blocks, total.
Blue = 30/3 = 10 blocks.
Red = (2/5)*30 = 12 blocks.