How do you do cross cancellation in fractions?

I believe this is what you mean by cross cancellation...

If we have something like
(x/7)(7x/4)(8)

On paper, it is easier to see, but the top (numerator) is x*7x*8 and the bottom (denominator) is 7*4. Since we have a 7 on the top and bottom, we can cancel those numbers. We also have an 8 on top and a 4 on bottom, so mark out the 4 and write a 2 in place of the 8.

Is that what you wanted?