I've done this question in a completely different way:
1. Draw a sketch of the lines
and
and the point A.
2. Determine the point of intersection of a and b:
3. Determine the equation of a line parallel to a through A
4. Determine the point of intersection of p and b:
5. You reach S if you go from R 2.2 units right and 2.2 units down. Now go from S 4.4 units right and 4.4 units down and you are at Q:
.
6. Determine the equation of the line AQ = l:
. Determine the point of intersection of
7. I've got