The slope of segment AC is (-6/22) = -3/11 .
The slopes of perpendicular lines are negative reciprocals, so
you know that the slope of the perpendicular bisector will be 11/3 .
The midpoint of segment AC is (7, -5) .
Now you have the slope of the perpendicular bisector, and
a point on it. You should be able to complete the equation now.
Notice how sneaky this question is. You don't need to know
point-B at all, and you don't even need to know that there's
any triangle. All you need to know is points A and C .
