①How often do you write your grandmother?
　(I often write her) once a month.

②How long is your summer vacation?
　I have about a month.

③What time does Sam usually leave home?
　He usually leaves at eight.

④How tall is Tom?
　He is 180 centimeters.

⑤How many tickets do they need?
　They need three.

あっているか、分かりませんが、参考程度でどうぞ。