invert and multiply
Hello 21_knipIf I read your attachment correctly, start with the 1 and the fraction at the bottom first, and write them over a common denominator; like this:
You now need 1 over this answer; that's
This is simply the reciprocal of the fraction: turn it 'upside-down':
Now you do a similar thing for the remaining 1 and this new fraction:
Watch that sign!
And so finally (as chiph588@ said) invert and mulitply:
I hope you followed all that.
Grandad