1/3 of plants on sale, of the plants on sale, 1/4 are rose bushes, 1/6 are spider plants and 1/6 are lilies, what fraction of the plants are discounted rose bushes, spider plants, or lilies
1/3 is your new whole, NOT 1. So take 1/4 of 1/3 + 1/6 of 1/3 + 1/6 of 1/3.
Pretend there are 180 plants. That would make 60 of them on sale. 1/4 of that is 15, 1/6 is 10 and 1/6 is 10. so that makes 35 out of the 180 is 7/36.
1/12 +1/18+1/18 or 3/36 + 2/36 + 2/36= 7/36.