"They live for eighteen months."
Translation:Vivono diciotto mesi.
Just curious, is there a reason why I cannot use "per" after vivono?...as in They live FOR 18 months.
Why would you want to use an extra word when you don't need to? The verb "vivere" can be translated as "to live for". In a previous post, someone kindly provided us with a few other similar verbs: pagare, cercare, aspettare, chiedere (pay, look, wait, ask FOR).
If it is the same as in Spanish, I'd say it's more natural to say this without "per", but that doesn't mean you can't use it at all. In fact, I just used it and Duo thought it was okay.