You have the problem:
4x+6 = 2x+4
Subtract 2x from both sides to get
2x+6 = 4
By subtracting 2x from the right side, you are only left with 4 on that side, and by subtracting 2x from 4x on the left side, you are left with 2x+6 on the left side.
Then subtract 6 from both sides to get
2x = -2
Subtracting 6 from the left side leaves you with just 2x on that side. By subtracting 6 from 4, you are left with -2 on the right side.
Finally, divide both sides by 2 to get
x= -1
Because the variable x had the coefficient 2, you had to divide it to get rid of the coefficient to find the value of x and because it was divided by 2 on one side, it had to to be done on the other to get the correct value of x which is -1.
