Each person will cost 3.50 for skates and 5.00 for food,
therefore, 3.50p + 5.00p = total cost for p people.
This number has to be at most 300, since that's Xian's budget (fairly baller for a birthday party).
Therefore,
Total cost for p people ≤ 300
Plugging in our cost for p people:
3.50p + 5.00p ≤ 300
Answer is D