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Maybe.
For ingress, you can define a policy that defines two classes and polices your traffic at your 3:2 ratio. Depending on your traffic, this may, or may not, provide the results you want.
I don't believe a 3550 supports any kind of shaping, so holding your traffic to 11 Mbps, is a problem.
If you're willing to run the interface at 10 Mbps, you can . . .
Use the interface command wrr-queue bandwidth, which allows you to define bandwidth ratios for your 4 egress queues.
PIck two of your four queues, map traffic to them, and assign them the 3:2 ratio you want.
A Cisco paper on 3550 queuing: http://www.cisco.com/c/en/us/support/docs/lan-switching/lan-quality-of-service/24057-187.html