Nicks nachos is selling 30 sodas for 20dollars. The ratio of the number sodas sold by Tony tacos to the number of sodas sold by Nicks nachos is 15/30 = 1/2
The ratio of the cost of sodas sold by Tony tacos to the cost of sodas sold by Nicks nachos is 10/20 = 1/2
So the number of sodas sold is proportional to the cost.
First you need to find the percent equivalent to that of the ratio. The ratio is 3:5. From there you would take the 3, and divide it by 5. 3/5=0.6. Apply that to the information that you are given: 8(0.6)=4.8.