7. A string has a total of 85 green, red, and yellow beads, arranged in the pattern “three greens, four reds, one yellow, three greens, four reds, one yellow, ......”. How many $\qquad$ red beads are there.

将上面的文本翻译成英文，请保留源文本的换行和格式，直接输出翻译结果。
Answer: 42
Exam Point: Periodic Problem
Analysis: Each group has 8, $85 \div 8=10$ (groups) 5 (remaining). Each group has 4 red ones, and the remaining 5 have 2 red ones, so there are a total of $4 \times 10+2=42$ (red beads)