Answer:
AM = 900
CI = 500
I have to be honest, this is the most ridiculously worded question of this type that I have ever seen... ask you teacher, why it was so important to force you to solve it using only one variable?
Explanation:
(AM) + (1400-AM) = 1400
2(AM) + 3(1400 - AM) = 3300
2AM + 4200 -3AM = 3300
-AM = -900
AM = 900
CI = 500