1 lemon to 2 waters will be proportional to what he Brandon needs so:
1 lemon / 2 water = x lemon / 12 water
Multiply by 12
And you get (1/2)*12 which is 6=x lemons
He needs 6 cups of lemons
Anything except pi is a rational number. So 9 and 7/10 is one or it could be a whole number