14, 16, 17, 19, 20
17 is the middle one so the answer is 17
Hope this helps :)
Blue triangle: perimeter is 4x+2+7x+7+5x-4, or, after simplification,
16x + 5
Red triangle: perim. is 2x-5+x+7+x+3 (and so on).
First, u do -9+8x-4+8
Then, U simplify. The answer is 8x-5
1/2 + 4x = 5x - 5/6
1/2 = x - 5/6
3/6 = x - 5/6
x = 8/6