Starting a new thread because I made a muck of the last attempt.

1 divided by u, + 1 divided by v, = 1 divided by f

I am required to find the value of V

If u = 4/5

If f = 2/3

V = !

4/5 - 2/3 = 2/15

2/15 =3 x 2=6=2

..........3 x 5 15 5

so is my value V = 5?

I am not sure and think there must be another way to ensure the numerator is equal to 1

Thanks

David