Here, we want to get the value of x
Looking at the image, the two angles form a right angle
What this mean is that they add up to give 90 degrees
Mathematically, we have it that;
[tex]\begin{gathered} 6x\text{ + 42 = 90} \\ 6x\text{ = 90-42} \\ 6x\text{ = 48} \\ x\text{ = }\frac{48}{6} \\ x\text{ = 8} \end{gathered}[/tex]