Larry used a pattern of colors to make a cube train. he used a red cube, a blue cube, a red cube, and another red cube before he started the pattern again. how many red cube did larry use?

I think 18 red cubes.
Explanation: A cube has 6 sides, so you would use the pattern 6 times. There are 3 red cubes in each pattern, you use the pattern 6 times, meaning 3 × 6, so the cube train has 18 red cubes. I hope this helps!