3. 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 = ?
5. 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 = ?
6. In the following problem, '=' stands for '÷' , '+' stands for '' , 'x' stands for '=', '' stands for '+' and '÷' stands for 'x'. Find the correct equation.
7. If (?) stands for division, (+) stands for multiplication, (÷) stands for subtraction and (×) stands for addition, which one of the following equations is correct?