Answer:
An unknown variable by reversing the process used to form the original equation.
Step-by-step explanation:
The opposite process rule says to solve for - an unknown variable by reversing the process used to form the original equation.
If an equation indicates an operation such as addition, subtraction, multiplication, or division, solve for the unknown variable by using the opposite process.
For example:
Lets say we have to find 
Here 25 is subtracted from both sides of the equation to isolate x.

we get x = 10
Check this : 
1st week - Lost 3 pounds = +3
2nd week - Gained 1 pound = -1
3+13 = + 22
So 22+3 = 25 25-1 = 24
So Tina lost 24 pounds in 13 weeks.
-25x + 40
Step-by-step explanation:
-8 (4x-5) + 7x
-32x + 40 + 7x
-32x +7x + 40
-25x + 40
Answer:
2x+12=24
first you subtract 12 from both sides
2x+12=24
-12. -12
The 12-12 should cancel itself, the rest of the equation you bring down to get
2x=12 (because 24-12=12)
Now you have 2x=12.
you then divide 2x by both sides.
2x=12
/2x=/2x
The 2x/2x cancels itself out so you then solve for 12/2x.
For this you just divide 12/2 which is 6!
x= 6 is your final answer.
to check this equation you can plug your number back into x to see if it is true! 2(6)+12=24.
6 times 2 is 12 and 12+12 is 24 so your answer (6) is true!
hope this helps! :D