The least number of boxes Sharon should buy is 5 boxes.
Step-by-step explanation:
Given,
Number of cards in box = 12
Number of stamps in packages = 20
We will find least common multiple of 12 and 20.
12 = 12,24,36,48,60,.....
20 = 20,40,60,80,....
The LCM of 12 and 20 is 60.
Now,
12 cards = 1 box
60 cards = 
60 cards = 5 boxes
The least number of boxes Sharon should buy is 5 boxes.
Answer: what do you need help with
Explanation: you never posted a problem
Answer:
12 hours
Step-by-step explanation:
Let Theo's siste can paint a fence in x times
Given.
Theo can paint a fence three times as fast as his sister can. Working together, they can paint a fence in 9 hours.

Apply cross multiplication

Theo’s sister to paint the fence in 12 hours.