Evaluate the following expressions using the indicated value of the variable/s:

1. x-12 ; x = 10

2. 5x - 24 ; x = 6

3. 6x - 7y ; x = 10 and y = 5

4. 7 + x ; x = - 13

5. 3x - y ; x -2 and y = - 18 ​