71.at the age of 在 岁时

71.at the age of 在....岁时
= When somebody was ... （years old.）
The boy is very clever ，he could speak five languages at the age of thirteen.
= The boy is very clever, he could speak five languages when he was 13 years old.
My sister got married at the age of 26 and now she has three children.
= My sister got married when she was 26 years old and now she has three children.