Four (1) class students plant trees, each plant one tree, there are 20 trees left, each plant two trees, the difference is 30 trees. How many students? How many saplings?

Four (1) class students plant trees, each plant one tree, there are 20 trees left, each plant two trees, the difference is 30 trees. How many students? How many saplings?

It will be easier for you to list the solutions of the equations. For example, suppose that there are x people in the class and Y trees,
x+20=y
2x-y=30
x=50,y=70

A total of 60 trees were planted by the four students. The trees planted by the first student were 1 / 2 of those planted by the other three students, and the trees planted by the second student were the same as those planted by the four students
A total of 60 trees were planted by the four students. The trees planted by the first student were 1 / 2 of those planted by the other three students. The trees planted by the second student were 1 / 3 of those planted by the other three students. The trees planted by the third student were 1 / 4 of those planted by the other three students. How many trees were planted by the fourth student?
It is necessary to specify the calculation process

First classmate 60 / (2 + 1) = 20
The second student 60 / (3 + 1) = 15
The third student 60 / (4 + 1) = 12
The fourth student 60-20-15-12 = 13

Class 4 and class 1 plant trees. If no one plants one tree, there are still 20 trees left. Each one plants two trees, with a difference of 30 trees. How many students and how many trees are there

Profit and loss
20 + 30 = 50 phase difference
2-1 = 1 reason
50 △ 1 = 50 people
50 × 1 + 20 or
50 × 2-30 = 70 trees