Okay, here we have this:
Considering the provided information, we are going to calculate how many minutes does it take per page to print, so we obtain the following:
Then from the statement we are going to calculate the time per page using the following formula:
Time per page = Total time / Total pages
Replacing:
Time per page = 7 minutes / 20 pages
Time per page = 0.35 minutes per pages
Finally we obtain that it take 0.35 minutes per page.