3x + 8 = 3x + []
Subtract 3x from both sides.
[] = 8
If you want no values of x, it can be any positive value other than 8.
If you want all values of x, the value must be 8.
If you want only one value of x, it is impossible because both equations have the same slope.
D is the answer because all you have to do is solve
Yes, is subtraction, to get their "difference".
first off, let's convert the mixed fractions, to "improper", and then subtract.

For the trapezoid, the equation used to solve for the area is,
A = (0.5)(b₁ + b₂)(h)
where b₁ and b₂ are the measure of the bases and h is the height. Substituting the known values above,
1224 = (0.5)(70.5 + 65.5)(h)
h = 18
Thus, the height of the counter top is 18 inches.