Question

You and your friend are running in a long racetrack. You pass the starting line at a constant 4 meters per second. Seventeen seconds later, your friend passes the starting line while running at 6 meters per second in the same direction, and at the same instant you increase your speed to 5 meters per second.

Answer 1

How long does it take for your friend to catch up with you?

$$s=4(17)+5t$$

$$s=6t$$

So,

$$4(17)+5t=6t$$

$$t=68\ s$$