Given:-
Most people shower at 8 a.m.
To find:-
How many people showered between 7 a.m. and 9 a.m.
In the given graph most people showerd is 22.
So that point is 8 am.
So the point before 22 and after 22 is 7am and 9am.
So to find the total people showered is,

So now the total people is 47 people.