I just took the quiz, the answer is A: Critical values=0.312; there is sufficient evidence to support a claim of a linear correlation between before-and-after weights.
Answer:
d=1
Step-by-step explanation:

Lets factor the denominator d^2 -2d-8
d^2 - 2d - 8 = (d-4)(d+2)

Now make the denominators same
LCD: (d-4)(d+2)

Denominators are same on both sides
So equate the numerators
-3d +3(d+2) = -2(d-4)
-3d +3d +6 = -2d +8
6 = -2d + 8
subtract 8 on both sides
-2 = -2d
So d=1
-(-2)^4 = 16
The - sign multiplies inside the bracket to a positive, 2^4 = 16
Since 800 is greater than 0.8 your statement would be 800>0.8