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 perimeter of a triangle is the sum of the lengths of its sides:

p = x + y + z
p = 9cm + 5cm + 8cm = 22cm

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° - 55° - 22° = 103°

So, d° = 22° + 103° = 125°

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° - 55° = 125°

The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)² : a = π r².

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.

4z - 4 = -7 - z
4z = -7 - z + 4
4z + z = -7 + 4
5z = -3
z = \( \frac{-3}{5} \)
z = -\(\frac{3}{5}\)