#### Answer

$|1-\sqrt{2}|=\sqrt{2}-1$

#### Work Step by Step

$|1-\sqrt{2}|$
Here, $\sqrt{2}\gt1$. This means that the substraction inside absolute value bars will result in a negative number. To express this quantity without the absolute value bars, we must change its sign.
$|1-\sqrt{2}|=-(1-\sqrt{2})=\sqrt{2}-1$