Mathematical Operations Questions

Find the missing number?

In a certain code language, '+' represents 'x', '-' represents '+', 'x' represents '÷' and '÷' represents '-'. What is the answer to the following question?
25 + 10 ÷ 240 x 16 = ?

If "+" denotes "divided by", "x" denotes "added to", "÷" denotes "subtracted from" and "–" denotes "multiplied by", then
54 + 162 – 18 x 12 ÷ 6 = ?

If 19 (36) 13 and 37 (81) 28, then what is the value of 'A' in 43 (A) 38?

If, 1*2= 1,
2*3= ­1 and
3*4= ­5, Then find the value of 7*9= ?

If 18 (9) 3 and 36 (30) 5, then what is the value of A in 19 (A) 18?

Select the number which can be placed at the place of ? in the following question

In a certain code language, '+' represents 'x', '-' represents '+', 'x' represents '÷' and '÷' represents '-'. What is the answer to the following question?
24 x 6 - 8 + 2 = ?