These problems only make sense if the percentage is by weight. To find the amount of salt, multiply the amount of solution by the percentage that is salt:
a) (80 g)(35%) = 28 g . . . . weight of salt
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b) (20 g)(17%) = 3.4 g . . . . weight of salt
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Comment on percent
You know that % means /100, so 35% = 35/100 = 0.35.
