ANSWER
[tex]x = 18 \degree[/tex]
EXPLANATION
A semicircle subtends an angle of 90° at the circumference.
From the diagram, the semicircle subtends an angle of (5x)° at the circumference.
We equate this angle to 90° and solve for x.
This implies that,
[tex]5x = 90 \degree[/tex]
Divide both sides by 5.
[tex]x = \frac{90}{5} [/tex]
[tex]x = 18 \degree[/tex]
