#### Answer

$b=6\text{ or }b=-6$

#### Work Step by Step

We start with the given equation: $8^2+b^2=10^2$
To simplify each of the constants being squared, we multiply them by themselves: $64+b^2=100$
In order to get the term with $b$ by itself, we subtract $64$ from both sides of the equation: $$64-64+b^2=100-64$$$$b^2=36$$To solve the equation $b^2=36$, we must perform the opposite operation of squaring, which is taking the square root, in order to clear the exponent: $$b^2=36$$$$\sqrt {b^2}=\sqrt {36}$$$$b=\pm6$$$$b=6\text{ or }b=-6$$