Yes.
70% of the customers buy a coffee drink and 30% buy food.
The sum of it is 100% already.
So 20% of it just another addition of information since it cannot exceed 100% of percentage (100% + 20% = 120%).
It also contains a subset for both percentage.
Step-by-step explanation:

Where Z is set of integer.
Answer:
75
Step-by-step explanation:
For this, you need to solve a proportion-
3.4 x
----- = -----
1.8 39.75
3.4*39.75=135.15
135.15/1.8= 75.0833.....
75.0833.. is rounded to 75