Why did scientists not know the 1989 san francisco earthquake was coming?

It's the simplest reason really, because the earthquakes can not be predicted. Talking about a short term prediction, yes, some occurrences give heads up that an earthquake is coming, though it is never a sure thing, but speaking long term, no earthquake can be predicted. Scientists know which are the places where earthquakes will most likely appear, but very often they are up to a surprise.

Joe ran 130 yards because 3 feet make 1 yard so using this ratio 390 feet make 130 yards.

Africans learned what the europeans wanted them to learn. instead of learning about african history and current information that could and would them they learned solely what europe wanted them to. and not everyone received the same education, some received better and others none.