jmc

We use the distance formula: $\sqrt{(-8-0{)}^2+(6-0{)}^2}=\sqrt{64+36}=\boxed{10}$.

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We note that the origin, the point $(-8,6)$, and the point $(-8,0)$ form a right triangle with legs of length 6 and 8. This is a Pythagorean triple, so the length of the hypotenuse must be $\boxed{10}$.