Question

solve for x.

Explanation:

Step1: Identify vertical - angle relationship

Vertical angles are equal. $\angle DHI$ and $\angle FHG$ are vertical angles. So, $7x + 18=81$.

Step2: Solve the equation for $x$

Subtract 18 from both sides: $7x=81 - 18$.
$7x = 63$.
Then divide both sides by 7: $x=\frac{63}{7}=9$.

Answer:

$9$