Answer:
10
Explanation:
1. Create a ratio of cows to days
7:30
*NOTE: The more cows, the less time it will take
2. Multiply 7 by 3 and divide 30 by 3
You would get 21 : 10
3. You have the answer!! :D
It will 10 days for 21 cows to graze the same plot of land.
Hope this helps :)
Have a nice day!