Question

a side of the triangle below has been extended to form an exterior angle of 143°. find the value of x.

Explanation:

Step1: Recall exterior - angle property

The exterior angle of a triangle is equal to the sum of the two non - adjacent interior angles. Let the non - adjacent interior angles be $x$ and $90^{\circ}$, and the exterior angle be $143^{\circ}$. So, $x + 90^{\circ}=143^{\circ}$.

Step2: Solve for $x$

Subtract $90^{\circ}$ from both sides of the equation: $x=143^{\circ}-90^{\circ}$.

Answer:

$53^{\circ}$