What is the justification for the step taken from line 2 to line 3?

The justification for the step taken from line 2 to line 3 is:

            Subtraction  property of equality ( as -2x is subtracted from both side of the equation)

We are given a steps for a proof as follows:

 Line 1--   3x+9-7x=x+10+x

Line 2--    -4x+9=2x+10

 ( From Line 1 to Line 2 we combined and simplified the like terms on each side of the equation )

 Line 3--   -6x+9=10

( From line 2 to line 3 we subtracted the variable term 2x on both side of the equation such that we are left with the variable term only at one side of the equation i.e. this property is known as subtraction property of equality)

  Line  4--    -6x=1

( Now line 4 is obtained by subtracting 9 on both side of the equation which is again known as subtraction property of equality)

Line 5--      x= -1/6

( Line 5 is obtained by dividing both side of the equation in Line 4 by -6 which is known as a division property of equality)

is only a line? i think so