Four students * * * planted 60 trees, the tree planted by the first student was 1/2 of the other three students, the tree planted by the second student was 1/3 of the other three students, and the tree planted by the third student was 1/4 of the other three students. How many trees did the fourth student plant?

The unit of this problem is 1, and the total number of trees is 1.

1/( 1+2)= 1/3

1/( 1+3)= 1/4

1/( 1+4)= 1/5

1- 1/3- 1/4- 1/5= 13/60

60*( 13/60)= 13 trees

The fourth student planted 13 trees.