Problem 63

A normal vector of the plane $OAB$ is $\overrightarrow{n}=(2,-2,1)$, and the given point is $P(-1,3,2)$.

The distance $d$ from point $P$ to the plane $OAB$ is given by the formula:

$$d=\frac{|\overrightarrow{n}\cdot\overrightarrow{OP}|}{|\overrightarrow{n}|}=\frac{|-2-6+2|}{\sqrt{2^2+(-2)^2+1^2}}=2$$

Therefore, the answer is $\boxed{2}$.

This problem can be solved directly by using the formula for the distance between a point and a plane.

This question tests the knowledge of how to calculate distances between points, lines, and planes in space, as well as the application of formulas, and it is a basic question.