We have to verify if 4/5 and 5/6 are eqauivalent to 2/3.
We can verify this dividing the numbers by 2/3, and if we get the value 1, then they are equivalent. If they are equivalent, then the fraction can be reduced up to 2/3, and this division will give us the value 1.
We start with 4/5:
4/5 is not a 2/3 ratio.
We continue with 5/6:
5/6 is not a 2/3 ratio.