Okay... seeing how this question was posted 5 days ago... i would have to say that it is beeing used to answer a summer homework question, due to the fact that i also have that same question(however it has the fact that i can't use zero), i ended up here. There are infinitly many answers because even if it is a negative number, it can still be even.
2+(-2)+20=20
4+10+6=20
(-1,000)+1,000+20=20
The negatives can cancle out the positve numbers