The first two are alike because you have to add 3 to each side for everything to come out even.
So we know that an average is the sum of the scores divided by the number of scores that were added together. In this case we are going to be dealing with 4 tests. So let's say x is the score for our fourth test. We can create this equation:

So then we need to simplify the top:

Then multiply by 4 on both sides to get rid of the denominator:

Then solve for x:

So now we know that Sam needs to score a 67 on the fourth test to have an average score of 50.
It is D linear explanation idek
B! If you draw the line of symmetry diagonally, you have two triangles
MP = P - M = (0, 5) - (5, 6) = (0-5, 5-6) = (-5, -1) |MP| = √((-5)^2 + (-1)^2) = √(25+1) = √26