the sum of all but one interior angle of a heptagon is 776°. what is the measure of the final interior…

Explanation:

Step1: Calculate the sum of interior angles of a heptagon

The formula for the sum of interior angles of an (n -)sided polygon is ((n - 2)\times180^{\circ}). For a heptagon ((n=7)), the sum (S=(7 - 2)\times180^{\circ}=900^{\circ}).

Step2: Find the measure of the unknown interior angle

Let the unknown angle be (x). We know that the sum of six angles is (776^{\circ}). Using the equation (S=\text{sum of six angles}+x), we substitute (S = 900^{\circ}) and (\text{sum of six angles}=776^{\circ}). Then (x=900^{\circ}-776^{\circ}).

Answer:

(x = 124^{\circ}), so the answer is (124^{\circ}) (the third option).