The points (-1,2) & (4,y) have a slope of -4/5. What is the y coordinate for (4,y).?
Slope=(y2-y1)/(x2-x1)
In your case:
x1= -1
x2=4
y1=2
y2=y
-4/5=(y-2)/[4-(-1)]
-4/5=(y-2)/(4+1)
-4/5=(y-2)/5 Multiply booth sides with 5
-4=y-2
-4+2=y
y= -2