I would recommend forgetting about where the x and y go and simply thinking about what it is you are trying to do.

You are estimating a proportion.

9/28 - There is your estimate of the proportion.

(9/28)*184 = 59 {and change} - There is your estimate of the number of blue ones.

If nothing else, this thinking about it stuff will refuse to let you build things backwards.

9/28 = x/184