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

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

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

If A = 1, E = 5, then HEAR = ?

If x means +, + means ÷, − means x and ÷ means −, then 8x7−8+40÷2 = ?