"哥哥"在英语中是"older brother"。

所以，如果你想用英语询问你的哥哥买了电脑，可以这样说：

Did your older brother buy a computer?

如果你想用英语告诉别人你的哥哥买了电脑，可以这样说：

My older brother bought a computer.

下面是一些其他关于"买电脑"的英文例句，并提供了中文翻译：

I'm going to buy a new computer next week. (我下周要买一台新电脑。)
She bought a used computer from a second-hand store. (她从二手店买了一台二手电脑。)
He's saving up money to buy a gaming computer. (他正在攒钱买一台游戏电脑。)
We need to replace our old computer, so we're looking to buy a new one. (我们需要替换我们的旧电脑，所以我们正在寻找新的电脑。)