Question

Question was provided via image upload.

Explanation:

Step1: Recall sum of interior angles of a quadrilateral

The sum of interior angles of a quadrilateral is $360^{\circ}$.

Step2: Set up an equation

We have $100 + x+80 + 57=360$.

Step3: Simplify the left - hand side

$100+80 + 57+x=237+x$.

Step4: Solve for x

$237+x = 360$, so $x=360 - 237=123$.

Answer:

$123$