Question

there is a triangle, one of its top angles is marked as $80^circ$, one of the bottom angles is marked as $50^circ$, and the other bottom angle is marked with a question mark, asking for the degree of this angle.

Explanation:

Step1: Identify triangle type

The figure is an isosceles triangle (two sides marked equal), so base angles are congruent.

Step2: Set up angle equation

Let the unknown angle be $x$. The sum of angles in a triangle is $180^\circ$.
$$x + 58^\circ + 58^\circ = 180^\circ$$

Step3: Calculate unknown angle

First sum the known angles: $58^\circ + 58^\circ = 116^\circ$
Then solve for $x$: $x = 180^\circ - 116^\circ$

Answer:

$64^\circ$