Can someone have a friendly hand and me on number 10

To solve this question and ones like it, we can do simple subtraction. We need to subtract the 1990 swim from the 1985 swim, we will see how much longer the 1985 swim was.

 22.40
-21.81
00.59

Using the math above, we can see that the 1985 swim was 0.59 seconds longer than the 1990 swim.

Iam unsure about what the proof is, therefore as much as wish to i can not.