P(r/w) is the probability of picking a red rose at first picking and a white rose at second picking.
P(w/r) is the probability of picking a white rose at first picking and a red rose at second picking.
P(r/w) =

×

=

P(w/r) =

×

=

Notice that the second fraction is out of 18 because the second picking of rose will be out of 18 since the first rose is not replaced.
P(r/w) equals to P(w/r)
I believe it is.... (2,2)or(4,4)
I believe it is B, but I'm still unsure !
What do you need help with?