Hace una semana que no sé nada de mis hijos. Si supiera que están bien, me quedaría más tranquila.I haven't heard from my kids for a week. If I knew they were okay, I wouldn't worry so much.
Quizá el Sr. Gómez sepa a qué hora es la reunión. - No creo. Si supiera a qué hora es, nos habría llamado para decírnoslo.Maybe Mr. Gomez knows what time the meeting is. - I don't think so. If he knew what time it is, he would have called to let us know.
Si supiera lo que me duele que usted me diga esas cosas, no me las diría.If you knew how much it hurts me when you say those things, you wouldn't say them.