Which must be true in order for the relationship △zyv ~ △xwv to be correct?

a. zy ∥ wx

b. ∠z ≅ ∠y and ∠w ≅ ∠x

c. zv ≅ vy and wv ≅ vx

d. ∠z ≅ ∠x and ∠w ≅ ∠y

Cherie works in retail and her weekly salary includes commission for the amount she sells. the equation s=400+0.15c models the relation between her weekly salary, s, in dollars and the amount of her sales, c, in dollars. interpret the slope of the equation.