Both are good options ❗ It is more common to give the time in positive. It is only common to use the time in negative to say: "menos quince"/"menos cuarto" o "menos cinco". Éxitos en sus aventuras idiomáticas ❗ Un saludo desde Colombia ❗

You can always be right by saying it as it goes. As in "son las nueve y cincuenta". You can't be wrong by saying it that way. The other option or potencial options are, for me, complicating language hahahaha... But some people use them, depending where you go. But again, you can't go wrong by just saying hours and minutes.

Two options are correct but the most comun is 'nueve menos 10'. My English is not so good I hope you can understand my answer

Hi! Greetings from Venezuela. :) Both are correct. "Son las nueve menos diez" is mostly used in Spain. In Latin American, we use "Son las ocho y cincuenta" or "Faltan diez para las nueve".

The both are correct but “Son las nueve menos 10” isn’t really used in Spanish, so use that it not bad, only peculiar