Coding and Decoding Questions

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

80 x 16 ÷ 4 + 2 - 8 = ?

If 9@7=4; 6@1=10; 7@4=6; then what is the value of 8@2=?

If 70*10 = -7, 50*5 = -10 and 10*5 = -2, then find the value of 80*1 = ?

If PONDERS is coded as ONCDQR, then how will MAT be coded as?

If MARBLES is coded as PDUEOHV, then how will GIN be coded as?

If A = 1, E = 5, then HEAR = ?

If in a certain language TEACHER is coded as QBXZEBO, then how is STUDENT coded in the same language?

Some equations have been solved on the basis of certain system. Find the correct answer for the unsolved equation on that basis. If 98-39-27=31, 87-38-34=20, then 79-25-12 = ?