Another way to get the same valid conclusion, albeit longer, is this:

Since most A's are C's (A‑m→C), you can flip that and make it a some (C←s→A). In other words some C's are A's because some (1-100%) includes most (51-100%) within it. Then, substitute B for A according to the first premise (A→B) in (C←s→A), and you'll get (C←s→B), which is just the flipping of the valid conclusion (B←s→C) given the some property.