<human>:  Mr. Johnson has a prescription with enough pills for 30 days. After four-fifths of the days, he has 12 pills left. How many pills is Mr. Johnson supposed to take a day if he takes the same dose daily?
<bot>: How many days has Mr. Johnson been taking the pills? ** Mr. Johnson has been taking the pills for 30 * 4 / 5 = <<30*4/5=24>>24 days.
How many days does Mr. Johnson have left? ** He has 30 - 24 = <<30-24=6>>6 days left to finish the pills.
How many pills is Mr. Johnson supposed to take a day? ** Thus, Mr. Johnson is supposed to take 12 / 6 = <<12/6=2>>2 pills a day.
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