Question

the math competition had 108teams on the first day. on the second day there were 10 less teams than on the first day how many teams were there on the second day

Answer 1

What you would do here is subtract.
The first day had 108 teams, and the second day had 10 less teams. 108-10 is 98, so there were 98 teams on the second day.

Answer 2

Just subtract 108-10 to get 98