2 Answers

3x-2(4x+5)=x+2,then x=?
You need to get the ?X? all by itself on one side of the = sign.  
Do the stuff in ( ) first.   3x - 2 (4x + 5) = x + 2
You can't add 4x and 5, because you don't know what x is, but you CAN multiply 2 x 4x and 2 x 5.  
3x - 8x - 10  = x + 2
3x - 8x is -5x
-5x - 10 = x + 2
Get the 10 away from the -5x.  You do this by adding 10 (but what you do on one side of the = sign, you must do on the other side)   -5x - 10 + 10 = x + 2 + 10
-5x = x + 12
NOW, get rid of the x + 12 by subtracting x.  Subtract x from BOTH sides: -5x -x = x - x + 12
-6x + 12.   Divide both sides by -6 to get x all by itself.  -6x/-6 = 12/-6
x = -2  (negative divided by negative = positive)
Check your work by putting -2 where "x" was in the original equation.  

x=1.5