The problem in Chapter 6, Exercise 1 should read:
Write a query to return the average weight of all touring bikes
 sold by Adventure Works Cycles that list for more than $2,300.
 Use the ProductSubCategory table to determine how you should
 filter these products.
The correct script would be:
SELECT AVG(Weight)
FROM Production.Product
WHERE ProductSubcategoryID = 3 and ListPrice > 2300