tommy likes to run up and down and "up" escalator. Going up, he can cover 30 steps in 6 seconds. Going down, it takes him 15 seconds to cover 30 steps. Find Tommy's rate (in steps per second) if the escalator stopped moving.

3 steps per second.

Step-by-step explanation:

Find the Unit Rates of each going up and down:

--> 30/6 unit rate is 5 steps per second.

--> 30/15 unit rate is 2 steps per second.

Now subtract them to get the amount if the elevator wasn't moving:

--> 5-2 = 3.