Answer:
[tex]\boxed {129\textdegree}[/tex]
Step-by-step explanation:
Both angles labeled, are actually Supplementary Angles (which two angles that add up to [tex]180\textdegree[/tex]). So, to find the missing measurement of an angle, which is the angle labeled in [tex]x[/tex], you need to take [tex]51\textdegree[/tex] and subtract it from [tex]180\textdegree[/tex] to get the missing angle measurement:
[tex]180\textdegree - 51\textdegree[/tex]
[tex]\boxed {129\textdegree}[/tex] (angle measurement for the angle labeled in [tex]x[/tex])
