We find some points on each line:

2x+y=11      y=x-1

  x|y         x|y   
  0|11        0|-1
  1|9         1|0
  5|1         5|4

We plot the points and draw a line through them, and
we look to see what point they cross at:



If we draw a green line from the point where they cross
down to the x-axis, and draw a red line from it over to
the y-axis, we see that it touches the x-axis at x=4
and the y-axis at y=3.  Those are the answers for the
first problem.

Edwin