15 divided by 2 1/2=6
Nestor can pot 6 plants in an hour. (I'm guessing that it said 2 1/2 hours)
Answer:
Second step: 2/2 does not give you 2.
It would be 2x + 1 - 4 = 3x - 3
Since he mess up on the second step, the following steps are also messed up

Hope you could understand.
If you have any query, feel free to ask.
Try .2 and see if it works.