Subject - verb agreement means that the verb must agree with its subject in person and number. To review person and number, let's look at some verb conjugations. He knows the answer She sees the solution.
Trains run down the track every day.
If you have been making this kind of subject-verb agreement error, you need to learn what endings are needed and to listen carefully for whether you have put on or left off an ending. Comments and suggestions can be sent to the UWC Online.