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

a = ½bh
a = ½ x 4 x 8 = \( \frac{32}{2} \) = 16

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° - 51° = 73°

So, d° = 51° + 73° = 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.

6y + 5 = \( \frac{y}{6} \)
6 x (6y + 5) = y
(6 x 6y) + (6 x 5) = y
36y + 30 = y
36y + 30 - y = 0
36y - y = -30
35y = -30
y = \( \frac{-30}{35} \)
y = -\(\frac{6}{7}\)

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.

You need to find the value of b so solve the first equation in terms of y:

2b + y = -8
y = -8 - 2b

then substitute the result (-8 - 2b) into the second equation:

5b + 2(-8 - 2b) = 5
5b + (2 x -8) + (2 x -2b) = 5
5b - 16 - 4b = 5
5b - 4b = 5 + 16
b = 21
b = \( \frac{21}{1} \)
b = 21