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 2 x 1) + (2 x 1 x 8) + (2 x 2 x 8)
sa = (4) + (16) + (32)
sa = 52

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

8a + z = -4
z = -4 - 8a

then substitute the result (-4 - 8a) into the second equation:

8a - 4(-4 - 8a) = -4
8a + (-4 x -4) + (-4 x -8a) = -4
8a + 16 + 32a = -4
8a + 32a = -4 - 16
40a = -20
a = \( \frac{-20}{40} \)
a = -\(\frac{1}{2}\)

To solve this equation, replace the variables with the values given and then solve the now variable-free equation. (Remember order of operations, PEMDAS, Parentheses, Exponents, Multiplication/Division, Addition/Subtraction.)

-3c(c - x)
-3(4)(4 + 6)
-3(4)(10)
(-12)(10)
-120

When solving an equation with two variables, replace the variables with the values given and then solve the now variable-free equation. (Remember order of operations, PEMDAS, Parentheses, Exponents, Multiplication/Division, Addition/Subtraction.)

A triangle is a three-sided polygon. It has three interior angles that add up to 180° (a + b + c = 180°). An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite (d = b + c). The perimeter of a triangle is equal to the sum of the lengths of its three sides, the height of a triangle is equal to the length from the base to the opposite vertex (angle) and the area equals one-half triangle base x height: a = ½ base x height.