Answer:
=34 minutes.
Step-by-step explanation:
Done according to my own understanding!
15mg - 7.25mg = 7.75mg
7.75mg / 20min = 0.3875mg per minute
7.25mg - 2mg = 5.25mg
5.25mg / 0.3875mg = 13.5483871 minutes
13.5483871 minutes + 20 minutes = 33.5483871 minutes
=34 minutes.