If 8% of c is equal to 12% of d, which of the following is equal to c + d?

Question

a)1.5d
b)2d
c)2.5d
d)3d
e)5d

I tried replacing the variables with numbers to make it easier. I came up with
8% of 600 = 12% of 400, both equal 48. And then 600 + 400 = 1000 but that's not one of the choices. I need help because I don't know how to approach the problem.

Answer 1

.08c = .12d
8c = 12d
2c = 3d
c = 3d/2

then c+d
= 3d/2 + d
= 3d/2 + 2d/2
= 5d/2 or 2.5d

in your specific case, you let
c = 600 and d = 400
then c+d = 1000 , like you had
now isn't 1000 = 2.5(400) or 2.5d ?

Answer 2

Thank you