We can divide out a common factor from both 6 and 8, which is a 2. This leaves us with (3*2)/(2*4), which simplifies to 3/4.
We can do the same thing with 9/12, but with 3 as our common factor. This leaves us with (3*3)/(3*4), which simplifies to 3/4, the same answer. So yes, these are equivalent.
Hope this helps!
