Adirect variation function contains the points (–9, –3) and (–12, –4). which equation represents the function?
y = –3x
y = – x/3
y = x/3
y = 3x

First, find the slope between the two points. 
Slope = y2-y1 / x2-x1
-4+3/ -12+9
-1/-3
1/3 is the slope of this equation. 
You do not have to go any further to find b or the y-intercept because it appears that b or the y-intercept is 0 in this case. 
y= 1/3x or in other words y= x/3

If you need an equation, it would be y=2x+8, y would be how long it grew, x being weeks.if you need how long he was asleep, it would be 4 weeks if he started with no beard, the equation would be x=8÷2if he did have a beard before hand, the equation would be 2w+x=8