23. This number-1 can divide 4 and 5 equally, so the minimum number is 4*5+ 1=2 1.

The maximum two digits that meet the requirements are 2 1+20*3=8 1.

The second picture is not clear.

27. Every column is even, so the smallest even number is 2. Therefore, there are at least 8*2= 16 people in row 8, and at least 12 = 24 people in row 8.

The least common multiple of 16 and 24 is 48, so there must be at least 48 people.