Answer && Step-by-step explanation:
Use what we know are given variables (answer choices)
we know middle is 15, 4x+7 must be > 15 plug in variables
7.5 makes it 35 but that is too big
4 is also > but it makes it slightly too big at 23 but when i divide by 3 i get 7.6, which mult 2 ~= 15
never the less, lets try it at top
4+3=7
make a triangle above 15, this will == half of 15 which is 7.5
7 is closest, I would guess 4 based on this alone.