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.

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.

A parallelogram is a quadrilateral with two sets of parallel sides. Opposite sides (a = c, b = d) and angles (red = red, blue = blue) are equal. The area of a parallelogram is base x height and the perimeter is the sum of the lengths of all sides (a + b + c + d).

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.

-7y - 4 = \( \frac{y}{2} \)
2 x (-7y - 4) = y
(2 x -7y) + (2 x -4) = y
-14y - 8 = y
-14y - 8 - y = 0
-14y - y = 8
-15y = 8
y = \( \frac{8}{-15} \)
y = -\(\frac{8}{15}\)

The volume of a cube is height x length x width:

v = h x l x w
v = 9 x 7 x 8
v = 504