You don't specify your geo location in your profile - I suspect however your based in Central / Eastern Europe and as such the delimiter in your locale is ; rather than , as per my example (UK).
(this is why it's a good reason to specify where on the planet you reside - there are differences in syntax)

Anyway... based on your last post and again assuming H,J,L are always in ascending order (ie J >= H and L >= J when populated) then:

=SUM(O8:S8)-MAX(H8,J8,L8)

If that's not always the case probably just easiest (given only 3 cells) to revert to an embedded IF

=SUM(O8:S8)-IF(SUM(L8);L8;IF(SUM(J8);J8;SUM(H8)))