Grade three+grade four+grade five = 126, and grade four and grade five are represented by grade three, that is, grade four = grade three+13.
Fifth grade = third grade +35 trees
So Grade Three+(Grade Three+13)+ (Grade Three +35)= 126.
3× Grade 3 +48= 126
Level 3 =( 126-48)÷3
You can get the following formula. The number of trees planted in the third grade is (126-13-13-22) ÷ 3 = 78 ÷ 3 = 26 (the reason for the formula has been mentioned earlier).
The fourth level is 26+ 13=39 trees.
The fifth level is 26+ 13+22=6 1 tree.
The answer is 26,39,61,please adopt it.