Answer
a. 78
Step-by-step explanation
Given that side PQ is tangent to circle O, then angle Q measures 90 degrees.
The addition of the three interior angles of a triangle is equal to 180 degrees. Applying this to triangle PQO, we get:
[tex]\begin{gathered} m\angle P+m\angle Q+m\angle O=180\degree \\ 12\degree+90\degree+x=180\operatorname{\degree} \\ x=180\operatorname{\degree}-12\degree-90\degree \\ x=78\operatorname{\degree} \end{gathered}[/tex]
