A trapezoid is a quadrilateral with one set of parallel sides.

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

-2b + x = -3b + 3x - 5
-2b = -3b + 3x - 5 - x
-2b + 3b = 3x - 5 - x
b = 2x - 5

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 w° = 30, the value of x° is 150.

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.

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 9 x 7) + (2 x 7 x 1) + (2 x 9 x 1)
sa = (126) + (14) + (18)
sa = 158