How to find the nth term of fractions ​

If the punch he is making has 80% cranberry juice and the rest ginger ale, we can say that there is 20% ginger ale. As 80% is 4 times 20% we can create the equation y (cranberry juice) = 4*x(ginger ale). So then if there is 2 liters of ginger ale, we substitute x for 2, and get y=4*2, and y=8, or 8 liters of cranberry juice. we can check this by seeing that the cranberry juice is 8 out of 10 total liters or 8/10, or 80/100 which is 80%.