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

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° - 38° - 45° = 97°

So, d° = 45° + 97° = 142°

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° - 38° = 142°

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.

5a x 3b = (5 x 3) (a x b) = 15ab

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:

x² + 3x - 31 = -x + 1
x² + 3x - 31 - 1 = -x
x² + 3x + x - 32 = 0
x² + 4x - 32 = 0

Next, factor the quadratic equation:

x² + 4x - 32 = 0
(x - 4)(x + 8) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (x - 4) or (x + 8) must equal zero:

If (x - 4) = 0, x must equal 4
If (x + 8) = 0, x must equal -8

So the solution is that x = 4 or -8

To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

7a³ + 6a³ = 13a³