This is not answer but Photomath is really helpful and it shows you step by step on how to solve it as well
In terms of its radius 
, the volume of the balloon is
The diameter 
is twice the radius, so that in terms of its diameters, the balloon's volume is given by
Differentiate both sides with respect to time 
:
The diameter increases at a rate of 
. When the diameter is 
, we have
or about 23,562 cc/min (where cc = cubic centimeters)
Mean=np
36=(0.12)n
n=300
300 students were surveyed.
That's the way I answer in my country but I'm not sure about this solution is correct in your school or not.
