Q: In this task, you're given a passage, further information available on a particular linked term from the statement, and an answer term. Your job is to generate a question that can use the information provided to obtain the given answer. You should use the information on both passage and link information to create the question. Note that the answer to the question should be exactly the given answer, and if the answer is none, the answer to the question shouldn't be obtainable from the passage or linked information.
Passage: In 1560 or 1561 Buchanan returned to Scotland, and by April 1562 was installed as tutor to the young Mary, Queen of Scots, who read Livy with him daily. Although he had remained Catholic throughout his support of the new learning and his strident criticism of the vices of the clergy, he now openly joined the Protestants Reformed Church and in 1566 was appointed principal of St Leonard's College, St Andrews, by the Earl of Moray. Two years before, he had received from the queen the gift of the revenues of Crossraguel Abbey. Though a layman, he was made Moderator of the General Assembly of the Church of Scotland in 1567. He had sat in the assemblies from 1563. He was the last lay person to be elected Moderator until Alison Elliot in 2004, the first female Moderator.
Link Information: Mary, Queen of Scots (8 December 1542 Answer: 20
A:
How old was Mary, Queen of Scots at the time the George Buchanan became her tutor?