since 4/25 = 1/4 that means ? /12 = 1/4 so in this case it would be 3 since 12 is divided by 3 to get to 4 for the denominator.
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.
group the first two and do foil like normal ignoring the "(x-3)"
you should end up with the answer x^2-16
now multiply (x^2-16) with (x-3)
that answer should be x^3-3x^2-16x+48