Need help Very much stuck!

Which values for a and b will create infinitely many solutions for this system of equations? ax-y=8 2x+y=b

Joseph haydn pet store offers wide variety of leashes for dogs. the store purchases one popular type of leash from its manufacturer for $4.38 each. joseph haydn pets marks up leashes at a rate of 238% of cost. what is the retail price of the popular leash?

Don't know how to find x given these segment lengths