The sum of the interior angles of a triangle is 180°:
180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 66° - 21° = 93°

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

sa = 2πr² + 2πrh
sa = 2π(2²) + 2π(2 x 2)
sa = 2π(4) + 2π(4)
sa = (2 x 4)π + (2 x 4)π
sa = 8π + 8π
sa = 16π

The first step to solve a quadratic expression that's not set to zero is to solve the equation so that it is set to zero:

c² - c - 17 = 2c + 1
c² - c - 17 - 1 = 2c
c² - c - 2c - 18 = 0
c² - 3c - 18 = 0

Next, factor the quadratic equation:

c² - 3c - 18 = 0
(c + 3)(c - 6) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (c + 3) or (c - 6) must equal zero:

If (c + 3) = 0, c must equal -3
If (c - 6) = 0, c must equal 6

So the solution is that c = -3 or 6

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

3b - 5x = -b + 9x + 4
3b = -b + 9x + 4 + 5x
3b + b = 9x + 4 + 5x
4b = 14x + 4
b = \( \frac{14x + 4}{4} \)
b = \( \frac{14x}{4} \) + \( \frac{4}{4} \)
b = 3\(\frac{1}{2}\)x + 1