"Why not in two days?"
Translation:למה לא מחרתיים?
In my opinion "למה לא ביומיים" and "למה לא בעוד יומיים" should both be accepted as well, but "למה לא ביומיים" has a different meaning than the accepted translation. "למה לא מחרתיים" means something like "Why not in two days from now" - used for example to set a new time for an appointment. "למה לא ביומיים" means something like "Why not in two days in total" - for example to set the amount of time it takes to finish a job (the speaker asks why it cannot be completed in two days).
So does the "מ" in "מחרתיים" mean from? I thought maybe the word "מחרתיים" came from combining "מחר" and "שתיים". Like saying two tomorrows. Maybe that's really daft. I didn't know any Hebrew until starting this course so all help is appreciated.