Point e is located at coordinates (-7, -5). point f is located at the coordinates (-2, 7). what is the length of ef?
a. 21 units
b. 17 units
c. 13 units
d. 15 units

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.