Between the hundreds and tens usually stands an and in English. This should be corrected...
I agree that most people put an 'and' there but technically you're only supposed to use it for numbers after the decimal so this sentence is correct.
This is also a correct answer: 7777
Dear DL: Of the two words for 'seventy' (bảy mươi ), the second word (mươi) is very hard to hear. It sounds like "mi."