'How much was last year's bonus?' should be accepted.
"How much was last year's bonus?" Exactly. I also agree.
This app has explicit possessives such as a 's block. Since there was no possessive, that answer is not accepted
How much was the bonus for last year should be accepted too. This kind of thing is frustrating..
It's not really idiomatic, and yeah, it sure is.
"How much was last year's bonus?" still not accepted. Reported 13th December 2018.
Still not accepted on 24th January 2019. Duly reported again...
is the 是 necessary here?
Yes, you can then use the same structure for the answer, substituting 多少 with the figure.
Why "last year's bonus" is wrong?????
Same as last Christmas's sales.
Multiple valid translations not accepted, this whole section is turning into a copy-paste job!