How do I understand perpindicular bisectors?

A line which cuts a line segment into two equal parts at 90°. Try this Drag one of the orange dots at A or B and note the the line AB always divides the segment PQ into two equal parts. When it is exactly at right angles to PQ it is called the perpendicular bisector.

Step-by-step explanation:

given the equation is 8+9z=-6, the first step would be to subtract the 8 from both sides:

8+9z-8=-6-8

since 8 minus 8 = 0, this would cancel out the 8. and since -6 minus 8 equals -14, the equation would look like this

9z = -14