Which graph represents a function?

In the equations, a and b represent the price per night for a room in hotel a and hotel b, respectively, w weeks after september 1 last autumn. what was the price per night in hotel a when it was equal to the price per night in hotel b? a = 240 − 20w b = 320 − 30w

Need this asap if anyone can i would be very grateful. if you could show workings that would really

Erin bought christmas cards for $2 each to send to her family and friends. which variable is the dependent variable?