Answer:
-30bc + 50bd
Step-by-step explanation:
3a + 5b/3c - 5d = 3a - 5b/3c - 5d
(3c - 5d)(3a - 5b) = (3a + 5b)(3c - 5d)
9ca - 15bc - 15da + 25db = 9ac - 15ad + 15bc - 25bd
9ca -15bc - 15da + 25db - 9ac + 15ad - 15bc + 25bd
9ca and -9ac and -15da and 15ad cancel each other out, so
-30bc + 50db is left
