Hi please Help ? I need help

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

Ineed someone to me answer my question i have to have this done and knocked out

Mike wants to make meatloaf. his recipe uses a total of 8 pounds of meat. if he uses a 3 to 1 ratio of beef to pork, how much pork will he use? enter your answer as a mixed number in simplest terms.