Verbal Reasoning - Mental Ability Questions

In the following question, which one set of letters when sequentially placed at the gaps in the given letter series shall complete it?
a_b_a_c_a_bc

If "A" means "plus", "B" means "divide", "C" means "multiply" and "D" means "minus", then 180 B 36 C 5 A 8 D 32 = ?

Select the missing number from the given responses

In the following question, select the related word from the given alternatives.
Mathematics : Formulas : : Chemistry : ?

P is the brother of Q. Q is the brother of R. P is the son of S. Based these three statements, much of the following statements cannot be definitely true?

A series is given with one term missing. Choose the correct alternative from the given ones that will complete the series.

Gw, Jt, Np, ?

A series is given with one term missing. Select the correct alternative from the given ones that will complete the series.

VW, XU, ZS, BQ, ?

If -2@-4 = -8, -1@-8 = -8 and -1@6 = 6, then find the value of -1@7 = ?