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° - 68° - 38° = 74°

So, d° = 38° + 74° = 112°

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° - 68° = 112°

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

p = x + y + z
p = 12cm + 15cm + 9cm = 36cm

To solve this equation, isolate the variable for which you are solving (b) on one side of the equation and put everything else on the other side.

-7b - 9y = 5b + 4y - 6
-7b = 5b + 4y - 6 + 9y
-7b - 5b = 4y - 6 + 9y
-12b = 13y - 6
b = \( \frac{13y - 6}{-12} \)
b = \( \frac{13y}{-12} \) + \( \frac{-6}{-12} \)
b = -1\(\frac{1}{12}\)y + \(\frac{1}{2}\)

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.)

The coordinate grid is composed of a horizontal x-axis and a vertical y-axis. The center of the grid, where the x-axis and y-axis meet, is called the origin.