To find the mass percentage of gold, we simply use the formula. So 49 grams of gold divided by the total mass of the solution, 49 grams plus 25 grams plus now we can't add kilograms to grams. So the first step is to convert this to grams. We get plus 500 grams. Now we multiply the whole thing by 100 to find the percentage, and we get 8.5%. The mass perceptive of gold is 8.5.