Question

let a equal the measure of angle a. the equation $360^{\circ}=a + 90^{\circ}+135^{\circ}+75^{\circ}$ represents the sum of the angles in the quadrilateral. find the missing angle measure by solving the equation.

Explanation:

Step1: Sum known angles

$90^\circ + 135^\circ + 75^\circ = 300^\circ$

Step2: Isolate $a$ via subtraction

$a = 360^\circ - 300^\circ$

Answer:

$60^\circ$