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_C_E_B_DE

What number should come in place of ?

In a certain code language, '+' represents 'x', '-' represents '+', 'x' represents '÷' and '÷' represents '-'. What is the answer to the following question?

50 + 3 ÷ 125 x 5 - 25 = ?

If CHANTED is coded as ZEXKQBA, then how will MAY be coded as?

If ALPHA = 36, BETA = 26 then DELTA = ?

If 8 θ 12 δ 6 = 60 and 13 θ 15 δ 11 = 74, then 18 θ 21 δ 15 = ?

In a certain code language, "STATION" is written as "5313462" and "RED" is written as "789". How is "TRAIN" written in that code language?

Find the missing number?