The two angles are what we call a linear pair because they form a straight angle when joined.
The sum of the angles in a linear pair is 180°.
Hence, we can say that:
[tex](x-1)+(5x+1)=180[/tex]
From this, we can solve for x.
Add x and 5x. Add -1 and 1.
[tex]6x+0=180[/tex]
Divide both sides by 6.
[tex]\begin{gathered} \frac{6x}{6}=\frac{180}{6} \\ x=30 \end{gathered}[/tex]
Therefore, the value of x is 30. (Option C).
