312 people bought balcony seats and 396 people bought ground seats.
Answer:

Step-by-step explanation:
Given

Required
How it'd be displayed on a calculator
Standard calculators, today are built to always convert huge numbers or extremely small number to scientific notations;
This was done to allow the calculator fit each values on its screen
is such a big number that it'll require the calculator to display it using scientific notations;
So, basically we have to convert
to scientific notaton;
This is achieved by replacing
with 
So,
is equivalent to 
Step-by-step explanation:
The number of subsets=2ⁿ where n=4 members
2ⁿ=2⁴=16
Number of proper subsets=2ⁿ-1
16-1=15