"Twenty-five men are sitting beside the tables."
Translation:Huszonöt férfi ül az asztalok mellett.
I feel that "ül" could also go at the end, if it's not accepted here then it's best to report it as an alternative answer .
I did report it myself, but now I see how the least important point of this sentence is exactly where they are sitting, so that comes last. I hope this is the correct way to look at it (word order)!
When you quantify an object it becomes singular. It's like saying in english: "I have three car". Or, because you are learning spanish: "Tengo tres rojo coche aparcado" (all singular, because you said "Three")