Verbal Reasoning - Mental Ability Questions

In a certain code language, '-' represents '+', '+' represents 'x', 'x' represents '÷' and '÷' represents '-'. Find out the answer to the following question.

13 ÷ 18 - 5 + 10 x 2 = ?

Students are sitting in a row in which the position of X is 17th from the left and that of Y is 14th from the right. If they interchange their positions, X's position becomes 7th from the left. How many students are there in the row?

Find the missing term in the following question:-

A series is given with one term missing. Choose the correct alternative from the given ones that will complete the series.
1, 7, 42, 210, 840, ?

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

Glacier, Waterfall, River, ?

From the given alternatives, select the word which CANNOT be formed using the letters of the given word.

Grandmother

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

DEF, ? , OPQ , VWX

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

DFI, JNS, TZG, ?