Huh?

6(2 + 4) - 1

2 x 3 + 1

Aline that intersects one of two parallel lines intersects the other also always sometimes never

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.

How is this equation completed? i cannot find any examples in the book.