16×20=320 (road)

Phase difference: 374-320=54 (road),

Every time 1 time, 2 1 tracks are more: 2 1- 16=5 (tracks),

Every time 1 time, there are 24 more tracks: 24- 16=8 (tracks),

So 54 is the sum of multiples of 5 and multiples of 8.

Because 54 is even, multiples of 8 are even,

So the multiple of 5 is an even number, so the single digit of the multiple of 5 is 0.

So the single digit of the multiple of 8 is 4, and among all the integers less than 54, only 24÷8=3 is consistent.

So 24 questions were asked three times.

There are (54-24)÷5=6 (times) 2 1 questions.

The problem with 16 is that 20-6-3= 1 1 (Tao).

Since 16 and 24 are multiples of 8, the number of times to write 2 1 should be 6 times or 6+8= 14 (times).

If the number of questions in 2 1 is 6, then the number of questions in 16 and 24 are 1 1 and 3, respectively.

If 2 1 give 14 times, the remaining 374-2 1× 14=80 is only given 5 times, so it is impossible.

So the correct answer is 16, 2 1, and the 24 questions are 1 1, 6 and 3 times respectively.

Answer: The questions 16, 2 1 and 24 were answered 1 1, 6 and 3 times respectively.