I think you’d need roughly a billion of them. Minus the 20 you have, of course.

They didn’t ask if it would be easy.

They didn’t ask if it it could be done without spending billions, or whether it would be feasible, i.e., practical, just whether it would be possible.

Do you mean one computer from 1985? No. There is no computer from that year that had enough RAM. If you mean all the computers from 1985, working together, then yes. You only need sufficient RAM, a Turing-complete machine, and probably some centuries to do it.