To multiply binomials, use the FOIL method. FOIL stands for First, Outside, Inside, Last and refers to the position of each term in the parentheses:

(y + 2)(y + 8)
(y x y) + (y x 8) + (2 x y) + (2 x 8)
y² + 8y + 2y + 16
y² + 10y + 16

You need to find the value of b so solve the first equation in terms of z:

8b + z = -2
z = -2 - 8b

then substitute the result (-2 - 8b) into the second equation:

-3b + 6(-2 - 8b) = 9
-3b + (6 x -2) + (6 x -8b) = 9
-3b - 12 - 48b = 9
-3b - 48b = 9 + 12
-51b = 21
b = \( \frac{21}{-51} \)
b = -\(\frac{7}{17}\)

The surface area of a cube is (2 x length x width) + (2 x width x height) + (2 x length x height):

sa = 2lw + 2wh + 2lh
sa = (2 x 7 x 2) + (2 x 2 x 8) + (2 x 7 x 8)
sa = (28) + (32) + (112)
sa = 172

The volume of a cube is height x length x width:

v = h x l x w
v = 2 x 4 x 9
v = 72

To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

8a + 4a = 12a