Final answer:
To find the fraction of the bill the fourth person pays, sum the fractions the first three persons paid (1/5, 1/4, 1/3), and subtract from the whole. The fourth person pays 13/60 of the bill.
Step-by-step explanation:
When the first person pays for 1/5 of the bill, the second person pays for 1/4, and the third person pays for 1/3, we need to find out what is left for the fourth person to pay. To do this, we calculate the total fraction of the bill that has been paid by summing the fractions:
1/5 + 1/4 + 1/3 = (12 + 15 + 20) / 60 = 47 / 60
Since the whole bill is equivalent to 60/60 (or 1 whole), we subtract the paid portion from the total to find the remainder:
60/60 - 47/60 = 13/60
The fourth person, therefore, pays 13/60 of the bill.