I need help its due soon please its precalculus

Question

You go to the doctor and he gives you 15 milligrams of radioactive dye. After 16 minutes, 4.5 milligrams of dye remain in your system. To leave the doctor's office, you must pass through a radiation detector without sounding the alarm. If the detector will sound the alarm if more than 2 milligrams of the dye are in your system, how long will your visit to the doctor take, assuming you were given the dye as soon as you arrived? Give your answer to the nearest minute.

You will spend    minutes at the doctor's office.

Answer 1

16/10.5 = m/14

10.5m = 224

m = 21 minutes