Use the equation method, okay?

(One student does half of the total number of the other three students), which means that the total number can be divisible by 3.

(B is one-third of the other three) means that the total can be divisible by 4.

(c is a quarter of the other three) means that the total can be divisible by 5.

The answer is 60 120 180 240. . . Judging from (Ding Zao 26 Flowers)

If the total number is 60, then A does 20b15c1220+15+12 = 47, then D does 13.

If the total number is 120, then A is 40 B 30 C 24 40+30+24=94 D 26.

So the total is 120.