Answer:
or 
.
Step-by-step explanation:
Suppose, the first side is a, the second side is b, and the third side is c. So:
→ a = s - 4
→ b = s
→ c = (s - 4) + 3
→ a + b + c = 15
First step, find the value of s
a + b + c = 15
(s - 4) + s + (s - 4) + 3 = 15
3s - 5 = 15
3s = 15 + 5
3s = 20

So, the third side is
c = (s - 3) + 4
c = s + 1
c = 

.
Happy to help :)
Im not sure what you are asking is there another part to the question.
Https://answers.yahoo.com/question/index?qid=20091104081842AAhdJmS
That might have your answer
if it is asking for compound interest your answer should be 49761.9