27 liters of paint... 3 liters per jug a total of 9 jugs meaning 9x3=27
This can be solved using the system of equations:
5500 = 1000c + 1500s
5 = c + s
As the first equation can have different combinations, it is the second equation that defines just how much acres or corn or strawberries(or mathematically, it defines the values of c or s in the first equation) there are. Therefore, the equation " 5 = c + s" is the constraint.