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.

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 5 x 6) + (2 x 6 x 5) + (2 x 5 x 5)
sa = (60) + (60) + (50)
sa = 170

The area of a rectangle is equal to its length x width:

a = l x w
a = a x b
a = 6 x 7
a = 42

The coordinate grid is composed of a horizontal x-axis and a vertical y-axis. The center of the grid, where the x-axis and y-axis meet, is called the origin.

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 + 8 < 9 + 3x
-7x < 9 + 3x - 8
-7x - 3x < 9 - 8
-10x < 1
x < \( \frac{1}{-10} \)
x < -\(\frac{1}{10}\)