This is because only one of the circles can be split into 4 sections due to their being an intersection in that circle. The rest may have both lines running through their length splitting them into 3 sections each.
To simplify the given equation, you want to combine like terms. Since both terms have x^8, we can add the coefficients and leave the x^8 3x^8-7x^8 (do 3-7) =-4x^8 so the answer is C
