A quadrilateral is a shape with four sides. The perimeter of a quadrilateral is the sum of the lengths of its four sides.

Parallel lines are lines that share the same slope (steepness) and therefore never intersect. A transversal occurs when a set of parallel lines are crossed by another line. All of the angles formed by a transversal are called interior angles and angles in the same position on different parallel lines equal each other (a° = w°, b° = x°, c° = z°, d° = y°) and are called corresponding angles. Alternate interior angles are equal (a° = z°, b° = y°, c° = w°, d° = x°) and 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°).

The surface area of a cylinder is 2πr² + 2πrh:

sa = 2πr² + 2πrh
sa = 2π(8²) + 2π(8 x 1)
sa = 2π(64) + 2π(8)
sa = (2 x 64)π + (2 x 8)π
sa = 128π + 16π
sa = 144π

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.

-4b - 4x = 6b + x - 7
-4b = 6b + x - 7 + 4x
-4b - 6b = x - 7 + 4x
-10b = 5x - 7
b = \( \frac{5x - 7}{-10} \)
b = \( \frac{5x}{-10} \) + \( \frac{-7}{-10} \)
b = -\(\frac{1}{2}\)x + \(\frac{7}{10}\)

The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)² : a = π r².