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#.
