In the following question, by using which mathematical operators will the expression become correct?
15 3_4_20 

If 25 @ 12 @4=296 and 15@6@3=87, then what is the value of 20@8@7=?

In a certain code language, '-' represents 'x', '÷' represents '+', '+' represents '÷' and 'x' represents '-'. Find out the answer to the following question.
15 - 6 + 10 x 3 ÷ 2 = ?

If '+' means '÷' ;  ‘÷’means ' - ' ; ' - ' means '×' ; '×' means '+' , then
8 + 2÷ 3- 4 x 6 =? 

In each of the following questions, which one of the four interchanges in signs and numbers would make the given equation correct?
( 3÷4 ) + 2=2 

Which of the following signs of equation are to be interchanged which will make the given equation correct?

5 + 6 ÷ 3 – 12 × 2 = 17

Some equations are solved on the basis of a certain system. Find the correct answer for the unsolved equation on that basis.
33 * 11 * 3 * 6 = 115 

Some equations are solved on the basis of a certain system. Find the correct answer for the unsolved equation on that basis.
7– 4 – 1 = 714, 9 – 2 – 3 = 932 8– 0–4 = ?