Solution
For this case we can create this notation:
x= number of fruit boxes
y= total weight
x y
0 0
1 3
2 6
3 9
4 12
5 15
6 18
7 21
8 24
9 27
10 30
11 33
12 36
13 39
14 42
15 45
16 48
17 51
18 54
19 57
20 60
21 63
22 66
23 69
Then the maximum number of pumplinks are 23