Question

can you please help me? around 5 minutes I asked this same question and nobody help me but it counts like a answered question​

Answer 1

3 hours

Explanation:

I'm going to do this a backwards way. Let's make a quick chart of how far each person has gone after each period of time.

The student is running 5 miles per hour (look at the graph, that's the slope) and the brother is going 15 miles per hour (given by the problem).

Brother leaves at the 2 hour mark; he hasn't moved AT ALL until after 2 hours is over.

Student: Brother:

After 1 hour 5 miles 0 miles (hasn't left yet)

After 2 hours 10 miles 0 miles (hasn't left yet)

After 3 hours 15 miles 15 miles

So after 3 hours, the brother catches upwith the student.