If two fractions are equivalent
then
the product of the numerator of the first fraction by the denominator of the second fraction must be equal to the product of the denominator of the first fraction by the numerator of the second fraction
so
In this problem we have
9/12 and 6/8
9/12=6/8
9*8=12*6
72=72 ----> is true
that means
The fractions are equivalent