Final answer:
Using the distance formula, we calculate that the distance between Mildred's house at (8,7) and John's house at (-1,5) is approximately 9.2 units, which means the correct answer is (c) 9 units.
Step-by-step explanation:
To find out how far apart Mildred's house at (8,7) and John's house at (-1,5) are, we will use the distance formula derived from the Pythagorean theorem, which states that the distance d between two points (x1, y1) and (x2, y2) in a coordinate plane is: d = √((x2 - x1)² + (y2 - y1)²).
Plugging in our values from the question, we get:
d = √((-1 - 8)² + (5 - 7)²)
d = √((9)² + (-2)²)
d = √(81 + 4)
d = √85
Since √85 is approximately 9.2, which is closest to 9 out of the given choices, the two houses are approximately 9 units apart.
Therefore, the correct answer to this question is (c) 9 units.