Question

Sylvanite is a mineral that contains 28.0 gold by mass. How much sylvanite would you need to dig up to obtain 43.0 of gold?

Answer 1

what does "by mass" mean?

Answer 2

i dont know what it means by that

Answer 3

Do you mean 28.0%? And 43.0 _grams_?
If so to both questions, then you are looking for what mass of sylvanite contains a total of 43.0 g of gold.
28% of m mass of sylvanite = 43.0 g of gold
28%m = 43
0.28m = 43
m = 43/0.28
m = 153.57
Since you are using 3 significant digits, answer is
154 g of sylvanite