Your answer is 20. Learn PEMDAS and it'll make this much easier. Parenthesis, Exponents, Multiply, Divide, Add, Subtract.
Plane R and plane P intersect at AB.
Planes are when 3 points that are not on the same line can be used to describe a plane. Plane P is horizontal and Plane R is vertical and these 2 planes intersect at line AB. Intersecting is where these 2 planes meet, therefore line AB is common to both planes.
The correct answer is (-9, -13)
p.s I already took the test and this was right
hope I helped :)
