Always try to factor in your first step if you can.
In the numerator of the first fraction, notice that we have
a greatest common factor of 4 so we have 4(3f - 4).
Now in the denominator of the second fraction, we have the difference
of two squares which can be factored as the product of two binomials.
So we have (3f + 4)(3f - 4) in the denominator.
So we now have 4(3f - 4)/16 · 5/(3f + 4)(3f - 4).
Now, cross-cancel.
Notice that the 3f - 4's cancel out completely.
Multiplying across the top and bottom, we get 20/16(3f + 4).
The 20 and 16 can reduce to 5 and 4.
So we have 5/4(3f + 4).
