Answer: 80 minutes
Step-by-step explanation: For this problem we will be using the ratio 2:8 which states that for every 2 cars, Victor can wash them in 8 minutes.
Basically, keep adding 2 to the left side of the ratio and keep adding 8 to the right side of the ratio until you get 20 cars on the left side.
2:8
4:16
6:24
8:32
10:40
12:48
14:56
16:64
18:72
20:80
So, in 80 minutes, Victor can wash 20 cars.