Since Sylvanite only contains 28% gold by mass, then to obtain 81.0 grams of gold, x amounts of sylvanite must be mined. To determine x, we divide 81 grams by 28%. This equation is shown below:
0.28X = 81
X = 81/0.28 X = 289.29 grams
Therefore, 289.29 grams of sylvanite must be dug up to obtain 81 grams of gold.
I believe you would have to multiply both 25 and 20 and what ever number you get dived by 100 if the numbers to high multiply aging or subtract the number (if it's wrong I'm really not good at my math I'm sorry)
