The book slipped from his hands and fell on the floor with loud noise, 20 eyes looked up at him and his face turned red..... Q: approximately,how many persons where at the library? •10 •20 •40
Let me answer this question within the goals of the site discussing English usage and not literature. This statement is confusing because it's not the normal way to say it. The correct way this sentence should be phrased is "20 pairs eyes looked up at him and his face turned red" Saying it any other way is intentionally unclear.