Mathematical Operations Questions

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

5 + 10 x 21 ÷ 5 - 15 = ?

In this question, some equations are solved on the basis of a certain system. On the same basis find out the correct answer from amongst the four alternatives for the unsolved equation.

15 x 26 = 6512

29 x 36 = 6923,

46 x 54 = ?

Find the missing number?

In a certain code language, '+' represents 'x', '-' represents '+', 'x' represents '÷' and '÷' represents '-'. What is the answer to the following question?
642 x 6 ÷ 25 + 4 = ?

Find the missing number in the given figure?

Find the missing number?

In a certain code language, '+' represents 'x', '-' represents '+', 'x' represents '÷' and '÷' represents '-'. What is the answer to the following question?
72 x 9 - 14 + 2 = ?

Find the missing number?