The Olympic gold medal contains 71.5% or gold by mass. This means a medal weighing 100 g has 71.5 g of gold in it.
It has to be determined how much gold can be extracted from a medal weighing 115 g.
The mass of gold in a medal weighing 115 g is 115*71.5/100 = 82.225 g
As the Olympic medal has 71.5% of gold by mass, the mass of gold in a medal weighing 115 g is 82.225 g.