A student claims that 2/3 = 6/7 because if you add 4 to both the top and the bottom of a fraction, the fraction does not change. How do you respond?

I am a bit confused. Don't you need to have a common denominator?

3 answers

http://www.mathsisfun.com/equivalent_fractions.html

Note that you need to use division or multiplication, not addition, to form or identify equivalent fractions.
The link you posted made it clear! Thank you Thank you!
You're very welcome!