Question 1200256
<font color=black size=3>
It's best to reduce 18/2 to 9.


Therefore, the answer would be y = (-1/2)x+9


As a check, plug the coordinates of (6,6) into that equation.
y = (-1/2)x+9
6 = (-1/2)*6+9
6 = -3+9
6 = 6
Both sides result in the same value, so we get a true equation. 
This confirms (6,6) is on the line y = (-1/2)x+9


Furthermore, the two lines y = 6-(x/2) and y = (-1/2)x+9 are parallel since they have the same slope -1/2.
{{{drawing(400,400,-3,8,-1,10,
graph(400,400,-3,8,-1,10,-100,6-(x/2),(-1/2)x+9),
red(circle(6,6,0.06)),
red(circle(6,6,0.08)),
red(circle(6,6,0.1)),
red(circle(6,6,0.12)),
red(circle(6,6,0.14)),
red(locate(6,6.62,"(6,6)"))
)}}}
y = 6-(x/2) in green
y = (-1/2)x+9 in blue


I recommend using a tool like Desmos or GeoGebra to graph.
</font>