This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
No, not everyone knows that a tab is set of fixed number of spaces. Because it isn't. It's just a character. And often displaying it results in displaying a number of spaces instead. But not a fixed number of spaces. A lot of output displays have tab stops at (for example) every 4 positions, so a tab character will be represented by between 1 and 4 spaces. At other times displaying a tab character has no effect at all, as for example in HTML.
But anyway that's all irrelevant if your question is how to replace the pair of characters (backslash, 't') by a single tab character. You do that like this:
That's a hint, so I will leave the other half for you.