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° - 43° - 55° = 82°

So, d° = 55° + 82° = 137°

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° - 43° = 137°

To factor a quadratic expression, apply the FOIL (First, Outside, Inside, Last) method in reverse.

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 < sign and the answer on the other.

4a - 4 < \( \frac{a}{-1} \)
-1 x (4a - 4) < a
(-1 x 4a) + (-1 x -4) < a
-4a + 4 < a
-4a + 4 - a < 0
-4a - a < -4
-5a < -4
a < \( \frac{-4}{-5} \)
a < \(\frac{4}{5}\)

To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

(8a)(3ab) - (7a²)(9b)
(8 x 3)(a x a x b) - (7 x 9)(a² x b)
(24)(a¹⁺¹ x b) - (63)(a²b)
24a²b - 63a²b
-39a²b

The area of a triangle is equal to ½ base x height:

a = ½bh
a = ½ x 5 x 7 = \( \frac{35}{2} \) = 17\(\frac{1}{2}\)