Answer: 16
Step-by-step explanation:
Subtract her age by her son’s age
Take your original equation 
and multiply both sides by
to remove the fractions. You are left with

So, 
Update: There is no numerical answer that can be found without being given a value for either x or y
33 and one third as a fraction would be either 33 1/3 or 100/3
16 because 8 rooms have 8-11, 5 rooms have 4-7, and 3 rooms have 0-3 guests.