45+10x = y
$45 -- stays the same no matter what so that's constant.
$10 -- this varies dependent on the number of vaccinations your dog needs, so you'd use a variable to represent the number of vaccinations (in this case i'm using variable "x").
so, for example if your dog needed 7 vaccinations, it would be: 45+10(7) = y -- answer being $115.
hey there!option a. is incorrect because it gives you the result ← ← ←
good luck on your assignment and enjoy your day!