Answer
$$b\approx 27.6$$
Work Step by Step
Use the Pythagorean Theorem:
$$c^{2}=a^{2}+b^{2}.$$
Rearrange terms:
$$b^{2}=c^{2}-a^{2}.$$
Substitute in $a=12.0$ and $c=30.1:$
$$b^{2}=(30.1)^{2}-(12.0)^{2}=906.01-144.00=762.01.$$
Take the square root of both sides and round to the nearest tenth:
$$\sqrt {b^{2}}=\sqrt {762.01}$$
$$b\approx 27.6.$$
