Answer: 15%
Explanation:
1) Percent decrease = (decrease / base value) × 100
2) Base value = number of people that went to the local swimming pool in the first week = 1,020
3) Decrease = net change in the number of people
Net change (decrease) = number of people that went in the first week - number of people that went in the fourth week = 1,020 - 867 = 153 people
Note that this number, 153, is equal to the sum of the changes: 183 + 110 - 140 = 153
5) % decrease = (153 / 1,020) × 100 = 15% ← answer