"Θέλω επτά βιβλία."

[Dmatafonov]

Always heard seven as εφτα in Cyprus - may be there is another prononcation allowed?

[D_..]

Both επτά and εφτά are correct, with the former possibly a bit more formal for official documents and the latter more common in everyday speech.

[BillDe]

But εφτα is still rejected here.

[mizinamo]

In a "type what you hear" exercise, you have to type exactly what you hear -- if the voice says /epta/, you have to type επτά; if it says /efta/, you have to type εφτά. Regardless of what you personally would say.

A bit like "aluminum" versus "aluminium" - both are correct English words but they are pronounced differently and in a "type what you hear" exercise you would have to use the version the voice says and not the alternative word with the other pronunciation.

[Tony979198]

In the Duolingo Tips and Notes 7 is listed as "εφτά" also...

[mizinamo]

Both εφτά and επτά are used and are both correct.

In a "type what you hear" exercise, you have to type the version that you hear.