Question 1:
The first error occured going from line 3 to line 4.
Why its incorrect:
instead of " ... -(2x-6) ... --> .... -2x + 6 .. .", he writes that
" ... -(2x-6) ... --> .... -2x - 6 .. .". In other words he multiplied by -1 without changing the sign.
The second error can be found going from line 5 to line 6.
Why its incorrect:
- 1 - 2x ≤ 4x - 8
- 1 - 2x + 1 ≤ 4x - 8 + 1
-2x ≤ 4x - 7
-2x -4x ≤ 4x - 4x - 7
-6x ≤ -7
Solving the inequality correctly:
5/12-(x-3)/6≤(x-2)/3
5/12-2/2*(x-3)/6≤4/4*(x-2)/3
5/12-(2x-6)/12≤(4x-8)/12
5-2x+6≤4x-8
11-2x≤4x-8
11 + 8≤ 4x + 2x
6x ≥ 19
x ≥ 19/6