Compare the number of friends at the beginning of a month and at the end of that month, if it decreased by 60% and then increased by 80%

28% decrease

Step-by-step explanation:

Let X be the no. of friends in the beginning

60% decrease = 40% left

0.4X

80% increase = 180% of previous

1.8 (0.4X) = 0.72X

72% of X

100 - 72 = 28

28% decrease