@GhostMutt More tins of veg means either 2 or 3 veg.
Prob(3 veg) is easy, because there's only one way of doing it: 5/9 * 4/8 * 3/7.
Prob(2 veg) is a bit harder: either VVT, VTV, or TVV. So 3*(5/9 * 4/8 * 3/7)
Add those together to get total prob
@GhostMutt You could work out the probs for VVT, VTV, and TVV separately, but it works out the same (try proving that!)
PS: what system is that?