Abackyard is 40.5 feet long and 25 feet wide. in order to install a pool, the yard needs to be reduced by a scale of 1/3 what is the area of the reduced yard?

To calculate for the area of the reduced yard, we may opt to calculate for the new dimensions which were already multiplied by the scale factor.
                   Length = (40.5 ft) x (1/3) = 13.5 ft
                   Width = (25 ft)(1/3)   = 25/3 ft
Then, multiply the dimensions in order to get the answer for the area of the yard.
                      Area of the yard = (13.5 ft)(25/3) = 112.5 ft²
Thus, the final area of the yard is equal to 112.5 ft².

4should be the last one n=4

Well if you have 20 bats you probably want 20 balls? you don’t have enough context to answer the question.