First, we need to find the slope:
m=rise/run OR
m=(2+2)/(-6-2)
m=4/-8
m=-1/2
second we need to find the equation for the line using point-slope form:
y-(-2)=-(1/2)(x-2)
to find "a" we plug in the given y value and solve for x (in this case x=a):
so, a=6 and the point becomes (6,-4)