An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite:

d° = b° + c°

To find angle c, remember that the sum of the interior angles of a triangle is 180°:

180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 56° - 40° = 84°

So, d° = 40° + 84° = 124°

A shortcut to get this answer is to remember that angles around a line add up to 180°:

a° + d° = 180°
d° = 180° - a°
d° = 180° - 56° = 124°

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.

9b - 4 = -5 - 8b
9b = -5 - 8b + 4
9b + 8b = -5 + 4
17b = -1
b = \( \frac{-1}{17} \)
b = -\(\frac{1}{17}\)

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

To multiply binomials, use the FOIL method. FOIL stands for First, Outside, Inside, Last and refers to the position of each term in the parentheses:

(y + 7)(y - 9)
(y x y) + (y x -9) + (7 x y) + (7 x -9)
y² - 9y + 7y - 63
y² - 2y - 63

The volume of a cylinder is πr²h:

v = πr²h
v = π(2² x 6)
v = 24π