Acertain ore yields an average of 64% iron. how much ore is needed to obtain 896 lb of iron?

In this case, the ore yield 64% iron and you need 896 lb of iron. From this description you can get an equation like this:

Iron= iron ore mass * 64%

Then, to get 896 of iron the calculation should be:
Iron= iron ore mass * 64%
896 lb= iron ore mass * 0.64
iron ore mass= 896 lb/ 0.64= 1400lb

257 grams h2o i think