step 1
Find the slope of the linear equation
we take the points
(-1,-1) and (2,8)
so
m=(8+1)/(2+1)
m=9/3
m=3
step 2
Find the equation of the line in sloe intercept form
y=mx+b
we have
m=3
point (2,8)
substitute
8=3(2)+b
solve for b
8=6+b
b=2
the equation is
y=3x+2
and the value of b is 2