Method 1: Everyone should plant at least 1 tree, which is 2 1 tree. The extra 12 tree belongs to the person who planted two or three trees. From the stem, we can know that the number of people who planted two trees is the same as that who planted three trees. If the number of people is set to X, then the person who planted two trees will plant 1 tree and three trees. Therefore, 1*x+2*x= 12, and the value of x is 4, that is, four people planted two or three trees, so it can be found that 1 tree is 13 people.

Method 2: It can be obtained by directly setting equations. According to the stem of the question, the number of people who plant two or three trees is equal, and they are all set as Y people, and those who plant one tree are set as X people. The following equations can be obtained: x+y+y=2 1, x+2*y+3*y=33, and y = 4, x = 65438.

Fill in the blanks with result 4!