A right angle measures 90 degrees and is the intersection of two perpendicular lines. In diagrams, a right angle is indicated by a small box completing a square with the perpendicular lines.

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 + 4)(y - 7)
(y x y) + (y x -7) + (4 x y) + (4 x -7)
y² - 7y + 4y - 28
y² - 3y - 28

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.

6a - 8a = -2a

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.)

-3a(a - y)
-3(-1)(-1 + 6)
-3(-1)(5)
(3)(5)
15

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 equal sign and the answer on the other.

3y + 5 = \( \frac{y}{8} \)
8 x (3y + 5) = y
(8 x 3y) + (8 x 5) = y
24y + 40 = y
24y + 40 - y = 0
24y - y = -40
23y = -40
y = \( \frac{-40}{23} \)
y = -1\(\frac{17}{23}\)