I am trying to figure out how to solve a problem such as "11C (subscript x-1)=5C^3 (subscript X)" can anyone help?

Question

A friend asked me how to do this and I have no idea.

Answer 1

₁₁C_(x-1) =  11! / [(x-1)!(11-(x-1))!]

but I'm not sure of what you mean the right side of your equation to be.