When solving an equation with two variables, replace the variables with the values given and then solve the now variable-free equation. (Remember order of operations, PEMDAS, Parentheses, Exponents, Multiplication/Division, Addition/Subtraction.)

An isosceles triangle has two sides of equal length. An equilateral triangle has three sides of equal length. In a right triangle, two sides meet at a right angle.

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:

z² + 22z + 75 = 5z + 3
z² + 22z + 75 - 3 = 5z
z² + 22z - 5z + 72 = 0
z² + 17z + 72 = 0

Next, factor the quadratic equation:

z² + 17z + 72 = 0
(z + 8)(z + 9) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (z + 8) or (z + 9) must equal zero:

If (z + 8) = 0, z must equal -8
If (z + 9) = 0, z must equal -9

So the solution is that z = -8 or -9

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° - 53° - 36° = 91°

So, d° = 36° + 91° = 127°

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° - 53° = 127°

The formula for circumference is circle diameter x π. Circle diameter is 2 x radius:

c = πd
c = π(2 * r)
c = π(2 * 15)
c = 30π