#### Answer

$-1$

#### Work Step by Step

We start with the given expression: $\pi r-(1+\pi r)$
To simplify an algebraic expression, we must eliminate any parentheses and combine like terms.
We use the distributive property to remove the parentheses: $\pi r - 1 - \pi r$
We use the commutative property to rearrange the expression such that like terms are next to each other: $\pi r-\pi r-1$
We combine like terms by subtracting: $0\pi r-1=-1$