There are two unknowns, the number of daisies and the number of lilies. Let be the number of daisies and be the numbers of lilies. We are told there is a total of 272 flowers, that is, the number of daisies plus the number of lilies is equal to 272. How can you state this mathematically?
We are also told "the number of daisies is twelve less than three times as many lilies." How can you state this mathematically?
Once you make these statements (or make an attempt to state them), you will have two equations in two unknowns, and we can guide you from there.