数学蓝皮64 题. 81 题求助~请高手帮忙

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64。 A rectangular floor is covered by a rug expect for a strip p meters wide along each of the four edges. If the floor is m meters by n meters, what is the area of the rug, in square meters?


这题，我，我看不懂红色的部分的意思。一个长方形的地板上铺了一个正方形的毯子，求毯子面积。
expect for a strip p meters wide along each of the four edges是嘛个铺法啊？
            
麻烦大家了,谢谢!
答案是(m-2p) * (n-2p)

81. If 方框 represents a digit in the 7-digit number 3, 62方框, 215, what is the value of 方框?

1. The sum of the 7 digits is equal to 4 times an integer.
2. the missing digit is different from any of the other digits in the number.

对条件1不是很明白,equal to 4 times an integer,这里的an integer是指0-9任意一个数字吗?