Exercise 3 Page 914

In case of triangles, when evaluating these expressions, we are supposed to obtain an angle measure of 60 degrees. Since the result in option A is not equal to 60, answer A is not correct. Now we can consider only three options: B, C, and D. Let's substitute 4 for n into these expressions.

For quadrilaterals, we are supposed to obtain an angle measure of 90 degrees after evaluating these expressions. Since the result in option B is not equal to 90, answer B is not correct. Therefore, we can consider only two options: C and D. Next, we will substitute 5 for n into these expressions.

For pentagons, we are supposed to get 108 degrees after evaluating these expressions. Since the angle measure in option D is not equal to 108, answer D is not correct. We can see that C is the only answer that can be correct. Let's check whether the expression from option C accurately finds the degree measure for hexagons, heptagons, and octagons.

After substituting 6, 7, and 8 into this expression, we obtained the correct values of angle measures. Since this expression best represents the degree measure of an interior angle of a regular polygon with n sides, the correct answer is C.