For parallel lines with a transversal, the following relationships apply:

• angles in the same position on different parallel lines equal each other (a° = w°, b° = x°, c° = z°, d° = y°)
• alternate interior angles are equal (a° = z°, b° = y°, c° = w°, d° = x°)
• all acute angles (a° = c° = w° = z°) and all obtuse angles (b° = d° = x° = y°) equal each other
• same-side interior angles are supplementary and add up to 180° (e.g. a° + d° = 180°, d° + c° = 180°)

Applying these relationships starting with x° = 140, the value of z° is 40.

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.

Perimeter is equal to the sum of the four sides:

p = a + b + c + d
p = 2 + 8 + 5 + 4
p = 19

To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

7a x 5b = (7 x 5) (a x b) = 35ab

To solve this equation, isolate the variable for which you are solving (a) on one side of the equation and put everything else on the other side.

-5a - 5x = -6a + x - 1
-5a = -6a + x - 1 + 5x
-5a + 6a = x - 1 + 5x
a = 6x - 1