"My friends have not spoken with him since Tuesday."

Translation: Meus amigos não falam com ele desde terça-feira.

[andylaw62]

why is the conjugation falam instead of falaram?

[Prancytime]

I think it's because the situation is still ongoing in the present. I'm kind of surprised that falaram isn't also accepted, though. It looks like it was at one point.
Maybe that's just a rule with desde.

[Davu]

In other sentences with "desde" the present tense has been used to convey the present perfect. So does "Meus amigos não falam com ele desde terça-feira" also work? [Edit: the model answer has changed since I wrote this comment.]

[Paulenrique]

Yes, indeed!

[LiskaDvacetdva]

Please I need to know why "falaram" used instead of "conversaram" is not right. There was another sentence with "eu falei com.." and there was correct translation "I talked with.. " Sorry, maybe I just don't get the difference between "talk" and "speak", they have various translations to Czech (my native) but they basically mean the same thing.

[FernandoSato]

I think you can use both in this sentence (both should be considered correct). In Portuguese, usually an interlocutor is implied when using "conversar" ("to talk"). Normally, a baby can "falar" (speak) but not "conversar" (talk), for example.

[ekvila]

Could you say "a terca-feira" or does it have to be just "terca-feira"?

[Paulenrique]

You have to use "terça-feira" once you have "desde" before it ;)

[LaugustoS]

Isn't 'não falam' present tense? the correct translation of 'they have spoken' is 'eles falaram', isn't it?

[Paulenrique]

"desde" usually requires present tense in Portuguese.