Procedure to solve the equation in one variable
-4 x-25= 8 x+15
Taking variable on one side and constant on another side of equation
- 4 x - 8 x = 15 + 25(When one quantity goes on other side of equation , the sign preceding it changes)
- 12 x= 40
x =

By looking at the solution described above , you can find yourself who has done the mistake between Becky and Tommy and can also identify the error and rectify it.