Alternatively, however, perform unknown numbers in straight line? (9)

I believe the answer is:
orthodoxy
'line?' is the definition.
(thesaurus)
'alternatively however perform unknown numbers in straight' is the wordplay.
'alternatively' becomes 'or'.
'however' becomes 'tho'' (I've seen this before).
'perform' becomes 'do' (both can mean complete an action).
'unknown' becomes 'x' (algebra).
'numbers in straight' becomes 'y' (I can't justify this - if you can you should give a lot more credence to this answer).
'or'+'tho'+'do'+'x'+'y'='ORTHODOXY'
Can you help me to learn more?
(Other definitions for orthodoxy that I've seen before include "Position of agreement with conventional standards" , "Accepted belief and practice" , "Traditional doctrine" , "Conventionality" , "Conformity" .)
