Rick R.
asked • 09/10/12what is the value of x?
Inactive Tutor answered • 09/27/12
You can move -x to the right side of the = and 12 to the left side of the equal. After you do that, this becomes.
3-12= x
Notice when you move, this changes the + or - sign.
so x = -9
Bill M. answered • 09/10/12
Doctor of Education, specializing in Artificial Intelligence.
3 - x = 12
Add x to both sides
3 - x + x = 12 + x
3 = 12 + x (- x and + x cancel each other out)
Subtract 12 from both sides
3 - 12 = 12 + x - 12
-9 = x (3 + -12 = -9)
Inactive Tutor answered • 09/10/12
Ok, we need to isolate x and there are two ways to do this. First, subtract 3 from both sides.
-3 + 3 - x = 12 - 3.
The two 3's on the left cancel and we have
-x = 9
Now, we multiply both sides by -1 so that x is by itself and we have x = -9!
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Inactive Tutor
Don't forget to check your work!
3-x=12 if x= -9
3-(-9)=12
any time I see a -(- i look at it as if it was a + because thats essentially what you have to do.
so 3 + 9 = 12
12=12 CHECKS OUT! way to go.
09/12/12