Solution: We are given that:
5 people can paint 7 walls in 21 minutes
Therefore, 1 person can paint 7 walls in minutes
Which means 1 person can paint 1 wall in minutes
Now, 3 people can paint 1 wall in minutes
Therefore, 3 people can paint 5 walls in minutes
For this case defining variables we have:
x: total amount of liters of potting soil.
y: number of liters of potting soil in each pot.
We have then to find the number of pots we use the following expression:
Substituting values we have:
Rewriting we have:
Rounding to the previous whole we have:
Answer:
Yao Xin can fill 18 pots