5. (10 points) Class 1 of Grade 4 used the class fund to purchase three types of stationery, A, B, and C, with unit prices of 3 yuan, 2 yuan, and 1 yuan, respectively.
It is known that the number of B type stationery purchased is 2 less than the number of A type stationery purchased, and the cost of A type stationery does not exceed half of the total cost. If the total cost for the three types of stationery is exactly 66 yuan, then the maximum number of A type stationery purchased is $\qquad$ pieces.
5. (10 points) Class 1 of Grade 4 used the class fund to purchase three types of stationery, A, B, and C, with unit prices of 3 yuan, 2 yuan, and 1 yuan, respectively. It is known that the number of B stationery purchased is 2 less than the number of A stationery purchased, and the cost of purchasing A stationery does not exceed half of the total cost. If the total cost for the three types of stationery is exactly 66 yuan, then the maximum number of A stationery that can be purchased is 11.  
【Analysis】Let the cost of purchasing A stationery be $x$ yuan, then B is $(x-2)$ yuan. Since the total cost for A, B, and C stationery is 66 yuan, the cost of A and B stationery $\leqslant 66$. Also, the cost of purchasing A stationery does not exceed half of the total cost. Solve the inequality accordingly.  
【Solution】9 Solution: Let the quantity of A stationery be $x$, and the quantity of C stationery be $y$, then the quantity of B stationery is $(x-2)$, so $3x + 2(x-2) + y = 66$,  
which simplifies to $y = 70 - 5x$,  
and $3x \leqslant \frac{66}{2}$,  
solving for $x \leqslant 11$,  
so the maximum number of A stationery that can be purchased is 11,  
Answer: The maximum number of A stationery that can be purchased is 11.  
Therefore, the answer is: 11.