Step I :
Underline key facts
Jack and Jill are filling up a small pool with water. For every two pails that Jack fills, Jill fills exactly one. If both of them fills the pool, with total of 36 pails. How many pails did Jack and Jill each contribute?
Step II :
Recognize the variable
For every two pails that Jack fills, Jill fills exactly one, now
If Jack will fill 2x pails then Jill will fill x pails
Step III :
Form Equations to solve
We also know, both of them fills the pool, with total of 36 pails.
So, mathematically speaking
Jack + Jill = 36
2x + x = 36
3x = 36
x = 12
Thus, Jack contributes 24 pails and Jill contributes 12 pails