A rancher has a square cow pen with side length x. He decides to change the shape of the pen while still using the same amount of fencing materials. The equation
(x + 10)(x - 10) = 300 represents the relationship of the new side lengths (in feet)
of the pen and its area (in square feet).
a. If 300 represents the area of the new cow pen, what do the expressions
(x + 10) and (x - 10) each represent?
b. Find x, the original side length (in feet) of the square pen. Show your reasoning.

Kevin has a spinner that has 10 equal sections and 2 sections of each color—red, blue, green, yellow, and purple. kevin spins the spinner 180 times. kevin determines about how many times the spinner will land on red or green, and his work is shown below. -kevin has the formula reversed; it should be the total number of sections over the number of red or green sections. -kevin should have used a 4 in the numerator because there are 2 red sections and 2 green sections. -kevin should multiply by the number of sections in the spinner rather than the total number of spins. -kevin calculated the prediction correctly and did not make any mistakes.