I have to add two number and get three for the sum. I am to lazy to do it myself so I need this now and quick

Too lazy? That's not a good thing for a teacher to hear :( You do the work and we will check it.

Is this for 3th grade? There are tons of possibilities. Pick any one mixed number. Your choice. The sky's the limit. Tell me what it is. I will tell you what to do next.

Most won't give the answer, as it is considered homework.
If the question was for the sum of 4, you could say 1 1/2 + 2 1/2, or 1 3/4 + 2 1/4, plus many others.
Hopefully this helps?

Perhaps the easiest way to do this is to think of a mixed number less than 3 and subtract it from 3. The remainder is another mixed number. So now you have two mixed numbers that add to 3.