Answer:
x = 117°
Step-by-step explanation:
We know:
The sum of the quadrilateral angles measures 360°.
Therefore we have the equation:
[tex]30^o+39^o+48^o+m\angle D=360^o\qquad(1)[/tex]
The sum of angles x and D is equal to 360°. Therefore we have the other equation:
[tex]x+m\angle D=360^o\qquad(2)[/tex]
From (1) and (2) we have:
[tex]x+m\angle D=30^o+39^o+48^o+m\angle D\qquad\text{subtract}\ m\angle D\ \text{from both sides}\\\\x=30^o+39^o+48^o\\\\x=117^o[/tex]
