In order to find the area of a rectangle, the formula is L*W (Length multiplied by Width). Our goal is to find these two measurements, so we will take the following steps:
1) Plot the coordinates on a graph (I have attached a visual guide)
2) Using the Pythagorean Theorem, or the Distance formula we can find the length and width:

3) We will use these values in the Area formula for a rectangle (L*W)
4) After solving the Area formula with the values retrieved from the Distance Formula we find that
the area is roughly 30 units squared.
First subtract the weight the dog weighs now to the weight he was:
48.9
- 29.7
------------
19.2
Then take the number you got which is the weight the dog gain in total, and divide it by the months the dog gained weight to get the average weight gained each month:
19.2/8 = 2.4
The average weight gain each month was 2.4 pounds.
Hope this helped you!