ANSWER
[tex]B.\text{ }18[/tex]
EXPLANATION
Let us make a sketch of the square:
Each angle in a square is equal to 90 degrees. This implies that:
[tex]5x=90[/tex]
Solve for x by dividing both sides of the equation by 5:
[tex]\begin{gathered} \frac{5x}{5}=\frac{90}{5} \\ \\ x=18 \end{gathered}[/tex]
The answer is option B.
