Answer:
100 blocks.
Explanation:
Let x represent number of blocks built by Gage.
We have been given that Colton was 5 times as fast at building the castle than Gage, so number of blocks built by Colton would be .
We are also told that it takes 120 blocks to build the castle. Since Colton and Gage were building a castle together, so number of blocks built by both will be equal to 120.
Hope it helped!