I don't really understand the question.

"A student heats 100.0g of copper(II)sulfate pentahydrate and obtains 58.2g of anhydrous copper(II) sulfate. What percent yield was obtained in this experiment? CuSO4 *5H2O + heat ==> CuSO4 + 5H2O"

I don't really understand what the percent yield is. And what I learnt in class, I only deal with one molecule not like anhydrous copper(II) Sulfate. So I've no idea what should I do and figure this question out.

Please help me.Thank you!:)

Well 1 mole CuSO4 from 1 mole CuSO4*5H2O would be 100% yield...

If you get less than 1 mole out, then it's less than 100% and you should be able to work out what percentage of the input you got out.

So how can I find the gram of CuSO4*5H2O ? Do I combine all the atomic mass or multiply?

Just find the molecular mass.