Translation:If you had introduced her to me last year, my life would have been very different.
Is it really a good idea to use only new verbs in a lesson supposed to introduce a new tense? Why heap one difficulty on top of another? I like to unravel things, but I fear some people will find this discouraging. It certainly isn't very good pedagogics. (I also have lots of nice things to say to Duo, but as often, the good stuff doesn't get told)
Can I ask about the arguments of tanıştırmak? In my (accepted) answer I had it as "[you] introduced me to him", but the translation given here has "[you] introduced her to me". Obviously there's a certain amount of reciprocity in introducing people to each other so the end meaning is not much affected, but technically should I be equating the Turkish accusative-argument with the English indirect object and the Turkish instrumental-argument with the English direct object with this verb, or vice versa?
"Eğer beni onunla geçen yıl tanıştırsaydın, hayatım çok farklı olurdu."
Translation: If you had introduced her to me last year, my life would have been very different.
If you introduced me to her last year, my life would have been very different.
Correct other English answer accepted by Duo.