9 because if you subtract 11 from 19 you get 9
Answer:make sure the value of x is positive
-check the solution to ensure it is a rational number
Step-by-step explanation: .
4 pack: 13/4=3.25
5 pack: 16/5=3.2
8 pack: 28/8= 3.5
the 5 pack is the cheapest per bulb so it has the best value