Answer
x = 20
Work Step by Step
Given that the sum of the angle measures of a quadrilateral is 360 degrees, we can add all the angles to find x.
(5x) + (4x + 10) + (80) + (90) = 360
(The 90 comes from the right angle, for a right angle is always 90 degrees).
Next, combine like terms and simplify:
(5x + 4x) + (10 + 80 + 90) = 360
9x + 180 = 360
Then, subtract 180 from both sides of the equation.
9x + 180 - 180 = 360 - 180
9x = 180
Finally, divide both sides by 9 to get x.
$\frac{9x}{9}$ = $\frac{180}{9}$
The 9's on the left side cancel out, so x = $\frac{180}{9}$
Simplify.
180 $\div$ 9 = 20
x = 20
