All snobbish girls are waste my time, but some girls aren't snobbish, so they must not waste my time. No strawberries are green, but some grapes are. So some grapes are not strawberries. Cherries are red, but some apples are not. So cherries aren't apples.
Some apples are green so, since all green apples are sour, some apples are sour.
Many motorcycles are loud. Harleys are loud, so Harleys must be motorcycles. Some long books are hard to understand. War and Peace is a long book, so it must be hard to understand. Some alcoholics should not become cops because they are irresponsible, and irresponsible people shouldn't be cops.