The slope of the line 4x - 8y = 11, is 1/2 (to see this rearrange it into the for

y=mx+c). So the slope of the required line is -1 divided by this ie -2.

So we seek the equation of a line through (6,6) of slope -2.

This can be written:

y = -2x + c,

and as it passess through (6,6) we have:

6 = -12 + c,

so c = 18, and the equation of the line is:

y = -2x + 18.

RonL