Question

what is the value of b?
work it out
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Explanation:

Step1: Identify the triangle type

Since two sides are marked equal, it is an isosceles triangle. In an isosceles triangle, the base - angles are equal. So, $\angle R=\angle P = 78^{\circ}$.

Step2: Use the triangle - angle sum property

The sum of angles in a triangle is $180^{\circ}$. Let $b$ be the vertex - angle. Then $b + 78^{\circ}+78^{\circ}=180^{\circ}$.

Step3: Solve for $b$

$b=180^{\circ}-(78^{\circ} + 78^{\circ})$.
$b = 180^{\circ}-156^{\circ}$.

Answer:

$24$