Please help me you will get 20 points

8

Step-by-step explanation:

It has to be 8 because I spent exactly 20 min helping u trying to find the answer

I think it has to be 8 I don't rlly get it but little bit of brain knowledge

i have i used to figure out the answer XD

step-by-step explanation:

points a and b are equidistant from the desired line, so the line you find by using them will go through point r.

using points other than a and b will give the desired line only if they are equidistant from r. if they are randomly located, the perpendicular line you create will not necessarily go through point r, hence will not be a solution to the problem.