Hi! This is actually a lot easier than you think :) let’s work through it! You actually have the hard part done already.
From where you are, now you need to count the shortest side (spoiler alert, it’s eight).
Know we know this length, recall it is a 30-60-90 triangle, so the longest side is double the shortest. Going by this rule, we know it is going to be 16.
Now we just add the values!
16 + 15 + 8 = 39
So.....
Answer (the perimeter) = 39!
*please note I assumed your top calculation of 15 was correct, so if it is actually not, just repeat the same steps and you should get the right answer!*