#### Answer

$b_{2}=\frac{2A}{h}-b_{1}$.

#### Work Step by Step

We start by dividing both sides by $\frac{1}{2}h$ to allow the eventual isolation of $b_{2}$. Now, we have $\frac{2A}{h}=b_{1}+b_{2}$. Subtract $b_{1}$ from both sides to isolate $b_{2}$, giving us $\frac{2A}{h}-b_{1}=b_{2}$.