We need to find an equation where the total of x and 4x equals 180 degrees. Why 180 degrees? Because if you draw a line perpendicular to the horizontal line you will get a degree and the top and bottom. And then added together makes 180 degrees.
x + 4x = 180
Combine like terms
5x = 180
Divide 5 into both sides
x = 36
So, x is equal to 36 degrees.