Use the point slope of line equation y=mx+c to calculate the slope of the line.

Here, the slope is 6 not -6.
Check whether the point (-1/2,5) is on the line.

Therefore, the point (-1/2,5) is on the line.
Compare the equation of the line y=6x+8 to that of y=mx+c implies,
c=8.
Here, the y intersept is 8 not 3.