Decrease of 28.6%.
Explanation:
The multiplier for a increase of a% is 1 + a/100.
The multiplier for a decrease of b% is 1 - b/100.
Decrease of 15%
1- 15/100 = 1- 0.15 = 0.85
Decrease of 16%
1- 16/100 = 1 - 0.16 = 0.84
Both:
0.85*0.84 = 0.714
Change:
The initial percentage is 100% = 1.
0.714 - 1 = -0.286
Negative, so a decrease
The answer is a decrease of 28.6%.