My Mum gets many letters.(Does? What? Who?)
Does your/my (смотря от какого лица говорить; склоняюсь к your) Mum get many letters?
What does your Mum get?
Who gets many letters?
Mary and Nick are from England.(Are? Where? Who?)
Are Mary and Nick from England?
Where are Mary and Nick from?
Who are from England?
She played chess yesterday?(?, What? Who?)
What did she play yesterday?
Who played chess yesterday?
Первый вопрос не указан, склоняюсь, что там Did:
=> Did she play chess yesterday?
Если вам понравился мой ответ, прошу поблагодарить. =)