if m<abc +<cbd = 90, M<abc=3x-5, m<cbd=x+1/2, then x=27 how do I solve for algebraic proof? Please help

I don't think I'm familiar with your nomenclature. I presume that <abc is "angle abc", but what does m<abc or M<abc mean?

Hm. Perhaps they mean : m - minor, M - Major

Well, either M and m were typos, I don't get 27...