Answer:
Team A.
Step-by-step explanation:
We know that Team A had 10 of its 12 members present.
We can write this as the following fraction:

We can convert this to a decimal by dividing the two numbers. Use a calculator:

And we can convert this to a percent by moving the decimal too places to the right and by adding a percent sign:

So, about 83.33% of members on Team A was present.
We know that Team B had 13 of its 15 members present.
We can write this as the following fraction:

Again, we can convert this to a decimal by dividing the two numbers:

Change this to a percent:

So, Team A had a participation rate of 83.33% while Team B had a participation rate of 86.67%.
So, the team that had the lesser percent of the team present at the tournament is Team A.
And we're done!