Answer :
We know 3 angles sum to 180 degrees {in a triangle]. Thus, we can write:
[tex]\angle1+\angle2+\angle3=180\degree[/tex]We are given Angles 2 and 3 and are told to find Angle 1. We substitute and do a bit algebra to figure Angle 1 out. The steps are shown below:
[tex]\begin{gathered} \angle1+\angle2+\angle3=180\degree \\ \angle1+2x+5x=180 \\ \angle1+7x=180 \\ \angle1=180-7x \end{gathered}[/tex]The last answer choice is correct.