The swimming pool is open when the high temperature is higher than 20 Celsius. Laney tried to swim on Monday and Thursday which was three days later. The pool was open on Monday but it was closed on Thursday. The high temperature was 30 Celsius on Monday, But decreased at a consistent rate in the next three days.

30° - 3d ≤ 20°

Step-by-step explanation:

We have to represent the rate of temperature decrease in degrees .We will represent this by "d" which stands for degree.

According to the question , temperature decreased at a constant rate in the next three days

Therefore , the total decreasing in three days = 3d degree i.e 3 *d=3d

Temperature on Monday = 30°

Then the temperature on Thursday is this = 30° - 3d

Since, The swimming pool is open when the high temperature is higher than 20°=≤20

= 30° - 3d ≤ 20°

This is the required inequality to determine the rate of temperature decrease in degrees Celsius per day, "d"from Monday to Thursday.