The mass of watch glass is 24.5 g , the mass of watch glass plus white crystals befor drying is 29.1g , and the mass of watch glass and white crystals after drying 27.9 , thus the mass of the white crystals is !????!

Answer 1

27.9g = mass watch glass + dry xtals
-24.5g = mass MT watch glass
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??? = mass dry xtals.

Answer 2

I don't understand the answer