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.

-c - 3 = \( \frac{c}{-7} \)
-7 x (-c - 3) = c
(-7 x -c) + (-7 x -3) = c
7c + 21 = c
7c + 21 - c = 0
7c - c = -21
6c = -21
c = \( \frac{-21}{6} \)
c = -3\(\frac{1}{2}\)

The area of a trapezoid is one-half the sum of the lengths of the parallel sides multiplied by the height:

a = ½(b + d)(h)
a = ½(8 + 7)(5)
a = ½(15)(5)
a = ½(75) = \( \frac{75}{2} \)
a = 37\(\frac{1}{2}\)

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.)

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.)

5c(c - y)
5(-9)(-9 + 4)
5(-9)(-5)
(-45)(-5)
225

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.