If a^2-b^2=648 and (a-b)=24, what is the value of (a+b) f.21 g.24 h.25 j.26 k.27

Sandy is upgrading her internet service. fast internet charges $20 for installation and $52.45 per month. quick internet has free installation but charges $57.45 per month. part 1 out of 2 complete the equation that can be used to find the number of months after which the internet service would cost the same. use the variable x to represent the number of months of internet service purchased.