Answer:
170 that is the answer hope it's right
Answer:
12 hours
Step-by-step explanation:
Let Theo's siste can paint a fence in x times
Given.
Theo can paint a fence three times as fast as his sister can. Working together, they can paint a fence in 9 hours.

Apply cross multiplication

Theo’s sister to paint the fence in 12 hours.
1/3 of 30 would be 10. So 10 students walk to school.