l > w + 3 --- first inequality
2 * (l + w) < 15 --- second inequality
Then, change the first inequality into the following by adding w, and multiply by 2
2 * (l + w) > 2 * (2w + 3)
So, now that,
2 * (2w + 3) < 2 * (l + w) < 15
2 * (2w + 3) < 15
2w + 3 < 7.5
2w < 4.5
w < 2.25
Usually question would ask for finding the maximum perimeter if l and w are whole number, in this case,
w = 2 and l = 5, so the maximum perimeter would be 14