Answer is 13-1/2 cups
Step by step
We know 1 cup is = 2/9 of a liter
We know we are working with 3 liters = how many cups
So first I want my 3 liters in a like denominator based fraction
1 liter is = 9/9 so 3 liters is = 27/9
I want to divide 27/9 by 2/9, the part of a liter that equals 1 cup
When I divide a fraction, I flip one fraction and multiply
27/9 x 9/2 = 243/18, simplify to 13-1/2 cups
Problem solved
You can check your work
Multiply 13-1/2 cups x 2/9
Change your whole number to a mixed fraction
27/2 x 2/9 = 54/18, simplify it equals 3 liters!