3. In each of the four packages, there are balls: white, red, yellow, and green. Each package has a tag, but none of them correspond to reality. Determine the color of the balls that are in the packages.
3. From the first condition, stating that the tag on each package does not correspond to reality, we can conclude that the yellow package does not contain yellow balls, the white one does not contain white balls, the red one does not contain red balls, and the green one does not contain green balls.

Assume that the white one has a red tag, then the yellow one is in the white or green package.

Assume that the yellow one is in the white, then the green one has a yellow tag, and the red one has a green tag.

Now let's assume that the yellow one is in the green, then the red one is in the white or yellow, etc.

To simplify the reasoning, you can use tables or graphs.

Answer: white in the red, yellow in the white, green in the yellow, red in the green.