String of operator

I had a technical round for an internship the ques was---------->

array of number are given like of n size 8,5,2,-2
in the array last term is RHS and rest is LHS
we have three operators (x,+,-)
now we have find the operator so that LHS=RHS
like in this array its 8-52=-2
so ans is -

order of number will remain same

3<n<7

how to do these type of ques or the approach, give me a hint I will try myself