Is 22/7 a repeating decimal? explain

Well, the way you wrote it ... 22/7 ... it's not a decimal at all.
It's an improper fraction.  But I understand what you mean.

Remember ... a fraction is a short way to write a division problem.
Whenever you see a fraction, it means

            (the top number) divided by (the bottom number) . 

If you take your pencil and paper, or your calculator, and do
the division '22' divided by '7' ... very easy to do; you really
should have done it on your own ... you get

                              3.142857...

That group after the decimal point ... the " 142857 " ... does
repeat forever.  So  22/7  does produce a repeating decimal.

The answer is why would a teacher ask that