Here we have fractions with different denominators, so must find and use the LCD. This LCD is (8)(3) = 24.
Rewriting the original problem,
3k/24 + 16/24 = 120/24. We can cancel the three equal denominators, obtaining:
3k + 16 = 120, or 3k = 104. Then k = 104/3, or 34 2/3 (answer d).
