This is a right triangle, as indicated by the right angle at one of the corners.

In any triangle, the sum of the interior angles is always $180^\circ$. Since one angle is $90^\circ$ and another angle is $63^\circ$, we can solve for $x^\circ$ using the following equation:

$x^\circ + 63^\circ + 90^\circ = 180^\circ$

Simplifying this:

$x^\circ + 153^\circ = 180^\circ$

Subtracting $153^\circ$ from both sides:

$x^\circ = 180^\circ - 153^\circ = 27^\circ$

Thus, $x = 27^\circ$.

Would you like more details or have any questions?

Here are five related questions:

1. What is the sum of the interior angles of any triangle?
2. How can we calculate the missing angle in a right triangle?
3. What are the properties of a right triangle?
4. Can a right triangle have an angle larger than 90 degrees?
5. What types of triangles exist based on their angles?

Tip: Always check that the sum of all angles in any triangle is $180^\circ$.