The midpoint of the line having the endpoints

and

is

basically average them
so given that the line has the endpoints of (-3,7) and (9,-2)
x₁=-3
y₁=7
x₂=9
y₂=-2
so the midpoint can be found by doing



the midpoint is
I’m pretty sure 7.583(repeating) will be the answer
Answer: Mine A
Step-by-step explanation: Mine A is further underground because elevation means height and when it’s shows a number that is negative that means underground. 225 is greater than 223. So Mine A is further underground.