when i marrid ,i was eight-een yeas old.

我结婚的时候，我十八岁。

当我结婚时，我才十八岁。
为了避免主语的重复，还可以翻译为：结婚时我十八岁。

when I married ,I was eighteen years old.
我结婚的时候才18岁

我18岁就结婚了。

When I Was Eight Years Old (英语作文)~

When I was eight years old, I lived in Henan. I finished my primary school .
I have many friends in Henan.
When I was eight years old, I deamed I would be a policeman in the future. But now I am a salesman.
When I was eight years old, my parents brought me to Zhenzhou ,and visited the Zoo. There were many animals . But I like monkey best.
When I was eight years old......

后者是对的。从句的世态应该喝主句保持一致。