Answer:
3s+15
Explanation:
let 's' be the length of the shortest side
-> twice as long as the length of the shortest side =2s
->length of the longest side to be three more than twice as long as the length of the shortest side = 2s + 3
-> the third side= 12 feet
p = s + 12 + 2s+3
p= 3s+15