I chose Expression 1 (P = 2a + 2b) to calculate the perimeter of the donkey's pen because it makes it easier to measure each side individually. It's important to have separate measurements for both sides, and this expression allows us to do that accurately. By using this expression, we can ensure that the total sum of all the sides is calculated correctly.

Can you make this sound like a 7th grader

I chose Expression 1 because it helps us measure each side of the donkey's pen on its own. It's important to have separate measurements for both sides, and this expression lets us do that accurately. So, we can make sure we calculate the perimeter correctly by adding up all the sides.