NEED HELP ASAP, DUE IN 3 MIN What is an interior angle of a triangle?

a) an angle created when the sides of the triangle are extended

b) an obtuse angle

c) an acute angle

d) an angle inside the triangle

Sanderson is having trouble with his assignment. his shown work is as follows: − 3 7 7 3 = − 3 7 × 7 3 = − 21 21 = −1 however, his answer does not match the answer that his teacher gives him. complete the description of sanderson's mistake. find the correct answer.