ABC has points A(-4,3),B(-4,1), and C (-2,1). After being reflected about the y-axis what is the length of BC

I’m stuck on this i don’t understand.

Find the solution of this system of equation -7x+y=-20 9x-3y=36

1. 2. ∠b and ∠y are right angles. 3.? 4.? which two statements are missing in steps 3 and 4? ∠x ≅ ∠c △abc ~ △zyx by the sas similarity theorem. ∠b ≅ ∠y △abc ~ △zyx by the sas similarity theorem. = 2 △abc ~ △zyx by the sss similarity theorem. = 2 △abc ~ △zyx by the sss similarity theorem.