Step-by-step explanation:
For no 1...
The range is [ -9, -7, 1]
For no 2....
The range is [-12, -10, -2]
For no 3.....
The range is [-11, -8, 4]
Length: 12
Width: 4 since 12x4=48 and length is 3 times as long as it is wide.
Answer:
7.0 < x < 7.6
X is the ideal pH of the swimming pool