4C/(10C-5D) + 2D/(6C-3D)

Question

Please include workings thx

Answer 1

The common denominator is (30C - 15D).

4C/(10C-5D) + 2D/(6C-3D)
= (12C + 10D)/(30C - 15D)
= 2(6C + 5D)/15(2C - D)
= (2/15)[(6C +5D)/(2C -D)].

I see no further simplifications.