The answer would be (-1) (7)(7)(7) because whenever -1 is multiplied by a number, it results in the opposite. The rule for integer multiplication is: same sign times same sign = positive different sign times different sign= negative
Since the key word is decreases, we know it is a negative times positive= negative. So any answer that does not have a negative answer will be eliminated.
To make it easy, all the other options are positive. So, that leaves you with the 3rd option.
First off, because the temperature is decreasing, that means the final answer would be negative, or we can also say that there would be a -1 to be multiplied by the change.
Each hour temperature changes by 7. The question also says that temperature keeps on changing for 3 hours. Therefore the temperature change would be by 3 7's, or 7+7+7.
Lastly, add the -1 from the beginning since it is a negative temperature change, the answer is (-1)(7+7+7)
