Given a sentence, fill out the missing word with a 'no' or a number (between zero and ten). You should write the numbers with english alphabet, like: four instead of 4.

Natural ytterbium is a mixture of ____ stable isotopes, with seven other unstable isotopes known.
seven

Some countries require passports to be valid for ____ months after expiry of the visa.
six

Young pandas mature very slowly and are almost ____ months old before they are weened.
six