Answer
$7.6 \text{ cm}$
Work Step by Step
One-half the perimeter is equal to the sum of the length and the width.
Thus,
$40.6(0.5) = w+ 2w- 2.5\\
20.3=3w-2.5\\
20.3+2.5=3w\\
22.8=3w\\
\frac{22.8}{3}=w\\
7.6=w$
Hence, the width is $7.6 \text{ centimeters}$.
