How to isolate algebraic fraction in this case

i have a question about of how to isolate an equation, when it has a multiplication in the denominator.

a/b/3 is same than a*(3/b)

but, when is:

a/(b/3 * 4/a)

If i want to isolate the 4/a that is multiplying the b/3 and in turn dividing to a, so how isolate only the 4/a ?

i have a question about of how to isolate an equation, when it has a multiplication in the denominator.

a/b/3 is same than a*(3/b)

but, when is:

a/(b/3 * 4/a)

If i want to isolate the 4/a that is multiplying the b/3 and in turn dividing to a, so how isolate only the 4/a ?