ANSWER
x = -7
EXPLANATION
The two given angles are vertical angles, because
The 80-degree angle is a corresponding angle of the blue angle, and the x+87 angle is corresponding to the red angle. Therefore, these two angles are vertical and hence they are congruent:
[tex]80=x+87[/tex]
Subtract 87 from both sides to solve for x:
[tex]\begin{gathered} 80-87=x+87-87 \\ -7=x \end{gathered}[/tex]
