How do you know that 21 over 30 is greater than 2 over 3

The problem deals with fractions comparison, lets do it:
21/30 > 2/3
we begin solving:
21 > (2/3)*30
21 > 2*10
21 > 20
therefore the proposed inequality is true, 21/30 > 2/3

You can solve as well getting same denominator for both fractions and comparing directly, in this case we need to get 2/3 to be divided by 30:
2/3 = (10/10)(2/3) = 20/30
So we have:
21/30 > 2/3
which is equal to:
21/30 > 20/30
and we compare directly because both fractions are divided by the same number, and we can see that the inequality is true.

Where is your question?

I’m confused as to what you are asking 66 2/3 percentage wise