15.6 - 12.3 me my homework is due in 3

3.3 would be the answer.

Step-by-step explanation:

This is because 15 - 12 is 3 and 6 - 3 is 3, therefore, when you add the decimal in between again, you get the answer.

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.