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 - 6)(y + 4)
(y x y) + (y x 4) + (-6 x y) + (-6 x 4)
y² + 4y - 6y - 24
y² - 2y - 24

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 4 x 5) + (2 x 5 x 9) + (2 x 4 x 9)
sa = (40) + (90) + (72)
sa = 202

You need to find the value of c so solve the first equation in terms of y:

2c + y = 8
y = 8 - 2c

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

9c + 1(8 - 2c) = 2
9c + (1 x 8) + (1 x -2c) = 2
9c + 8 - 2c = 2
9c - 2c = 2 - 8
7c = -6
c = \( \frac{-6}{7} \)
c = -\(\frac{6}{7}\)

To solve this equation, repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the > sign and the answer on the other.

7x - 7 > -6 - 5x
7x > -6 - 5x + 7
7x + 5x > -6 + 7
12x > 1
x > \( \frac{1}{12} \)
x > \(\frac{1}{12}\)

The first step to solve a quadratic equation that's set to zero is to factor the quadratic equation:

a² + 10a + 21 = 0
(a + 3)(a + 7) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (a + 3) or (a + 7) must equal zero:

If (a + 3) = 0, a must equal -3
If (a + 7) = 0, a must equal -7

So the solution is that a = -3 or -7