A rhombus is a parallelogram with four equal-length sides. A square is a rectangle with four equal-length sides.

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

sa = 2πr² + 2πrh
sa = 2π(9²) + 2π(9 x 9)
sa = 2π(81) + 2π(81)
sa = (2 x 81)π + (2 x 81)π
sa = 162π + 162π
sa = 324π

A circle is a figure in which each point around its perimeter is an equal distance from the center. The radius of a circle is the distance between the center and any point along its perimeter. A chord is a line segment that connects any two points along its perimeter. The diameter of a circle is the length of a chord that passes through the center of the circle and equals twice the circle's radius (2r).

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.

-2a + 4 = \( \frac{a}{-7} \)
-7 x (-2a + 4) = a
(-7 x -2a) + (-7 x 4) = a
14a - 28 = a
14a - 28 - a = 0
14a - a = 28
13a = 28
a = \( \frac{28}{13} \)
a = 2\(\frac{2}{13}\)

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.

-3b - x = -6b + 7x + 8
-3b = -6b + 7x + 8 + x
-3b + 6b = 7x + 8 + x
3b = 8x + 8
b = \( \frac{8x + 8}{3} \)
b = \( \frac{8x}{3} \) + \( \frac{8}{3} \)
b = 2\(\frac{2}{3}\)x + 2\(\frac{2}{3}\)