Question 1062560
0.2A = B  —> A = 5B      
0.4B = C  —> B = 2.5C 

I assume the problem wants the answer in terms of C:
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(0.6)(A+B) = 
(0.6)(5B + 2.5C) =           (substituted for A and B)
(0.6)(5(2.5C) + 2.5C) =    (substituted for B)
(0.6)(15C) =
9C