Write an equation of a line with the given slope and y-intercept (8,1)m=-1/2

Slope intercept form is y=mx+b 
first plug in m
y=-1/2X + b 
 now plug in the point (8,1) for the x and the y
1=-1/2(8) + b

now you need to solve for b
simplify
1=-4+ b
add 4
5=b

now that you know b
you can plug it into the equation along with the m

so the answer is 
y=-1/2X + 5