The problem of free canteen in hotel

Meal cards are made of paper with a grid. Meals are divided into main meals (Chinese food and dinner), 3 yuan/meal, and auxiliary meals (breakfast and midnight snack), 1.5 yuan/meal. All employees are charged for meals, and 15 yuan is subsidized for meals every month. According to the actual number of meals per month, the expenses are counted and deducted from the salary. For example, the expenses for employees to eat are that 18 yuan should deduct 3 yuan from his salary in addition to 15 yuan's food subsidy; The expenses for employees' meals are 1 yuan, so they can get food subsidies to 5 yuan every month.