Verbal Reasoning - Mental Ability Questions

In the following question, by using which mathematical operators will the expression become correct?
30 ? 6 ? 4 ? 5 ? 4

Select the missing number from the given responses:

In a certain code language, "NATURE" is written as "TANURE". How is "LISTEN" written in that code language?

In the following question, select the missing number from the given series.
1, 3, 6, 10, 15, ?

In a row of boys, Amit is ranked 12th from top and Ratan is 15th from bottom. They interchange their position. Ratan now becomes 37th from bottom. How many total boys are there in the row?

In a certain code language, "RUMOUR" is written as "MURRUO". How is "RACKET" written in that code language?

Select the related word/letters/number from the given alternatives. E : V : : D : ?

Deepak introduces Raju saying, "He is the husband of the granddaughter of the father of my father." How is Raju related to Deepak?