Answer:
1 / (x² + 6x + 8)
Step-by-step explanation:
(x + 4) / (x² + 5x + 6) * (x + 3) / (x² - 16)
= (x + 4) / (x + 2)(x + 3) * (x + 3) / (x + 4)(x - 4)
↑ factor x² + 5x + 6 ↑ factor x² - 16 using difference of squares
= 1 / (x + 2) * 1 / (x - 4) ← x + 4 and x + 3 cancel
= 1 / (x + 2) * (x + 4) ← multiply
= 1 / (x² + 6x + 8) ← expand
