What line if any are parallel

What is the area of the triangle 10 13 12

Which must be true in order for the relationship △zyv ~ △xwv to be correct? zy ∥ wx ∠z ≅ ∠y and ∠w ≅ ∠x zv ≅ vy and wv ≅ vx ∠z ≅ ∠x and ∠w ≅ ∠y

How do you figure out which order to do two step equations in? like which thing do you subtract/add/multiply/divide first? i understand that you do the opposite of whatever's shown on the opposite side, but when?