A-level "weird" combination (3 A-level subject included further math)

i have just done my SPM ( equivalent to year 11 program in my country) and wish to go for A-level , since i am not taking any science subject in my SPM , i can't take any bio phy chem in my A-level . As i love math and also econs (more on math ) , i wish to take math , fuether math and econs in my A-level , are this combination OK? I hope to go for math and econs related degree such as mathematics with economics or something . Is this combination ok? seems like some uni dont allow.

Which unis don't allow it?

like NTU singapore? and a lot of pre-u college in my country dont even allowed FM be a third subject.

Oh, sorry. I just automatically assumed you were talking about UK universities (of which I don't know any which would disallow those three subjects for a mathematically-focussed degree).
If your question is about universities outside the UK, then I'll step aside and let others answer (as I have no knowledge of non-UK universities).

basically all UK uni allow？just extra infor