A liter of water weighs a kilogram so 15 mg/kg = 15 ppm on a mass over mass basis. If that is the flavor of ppm you want, done. But ppm can also be computed on a volume basis, molar ratio, etc. It is better tio use a clear form with units that identifies the basis such as mg/kg.
Serena Williams knocked off Lucie Safarova in the final of the women's draw at the French Open, and Bovada has her listed as the clear favorite on the odds to win Wimbledon this year; Williams sits as the 7/4 chalk on those betting lines.
8 is enough: Federer gets record-breaking Wimbledon title. Switzerland's Roger Federer kisses the trophy after defeating Croatia's Marin Cilic to win the Men's Singles final match on day thirteen at the Wimbledon Tennis Championships in London Sunday, July 16, 2017.