[Terretta]

The field can be perfectly even. If you have 15 guys and 5 girls enter the field, you'll find more men attain the goal.

So: “Solve the problem at the left.”†

This means for most leverage, meaning best results with least cost and least waste, intervene in a system at the earliest stage that can make a difference.

† The metaphor is assuming production lines flow left to right. RTL cultures can say "solve the problem at the right" which has the advantage of both metaphor and pun!