Can some one pls help me fill is the square pls help

Me ! write an equation for the interior angles of this triangle that uses the triangle sum theorem

Which of these equations, when solved, gives a different value of x than the other three? a9.1 = -0.2x + 10 b10 = 9.1 + 0.2x c10 – 0.2x = 9.1 d9.1 – 10 = 0.2x

What is not true about kl and mn? what is mn? (show your work)