If X equals 100 points and Y equals you, and Z equals no effort then, Y+Z= X, correct? (report/ delete question when done)

Match the equivalent expressions. x - 3y + 12 12 - 3y - 2x + x + 2x 3x + 2y - 2x + y + 12 3y + 12 3x + y - 12 4y + 3y + 3x - 6y - 10 - 2 x + 3y + 2x - 3x + 7 + 5 x + 3y + 12 5 + 2y + 7x - 4x + 3y - 17

What is the value of x when x + 7 = 21?

What is the missing reason in the proof? segment addition congruent segments theorem transitive property of equality subtraction property of equality?