Answer
$y=-\frac{1}{2}x+3$
Work Step by Step
The equation of the tangent line to the graph of $B(x)$ at a point $x=a$ is formulated by:
$y-B(a)=B'(a)(x-a)$
Then, at $x=6$ the tangent line to the graph of $B(x)$ has the following equation.
$y-B(6)=B'(6)(x-6)$ (Use the given properties)
$y-0=-\frac{1}{2}(x-6)$
$y=-\frac{1}{2}x+3$
