let's keep in mind that, there are 1000 grams in 1Kg, KILO=thousand.
so on the first week she lost 2Kg and 810g, namely 2000g + 810g = 2810 grams.
second and third weeks, 1Kg and 48g, or 1000g + 48g = 1048grams each week and so on.
[tex]\bf \stackrel{\textit{before the diet}}{x}~~~~=~~~~\stackrel{\textit{today's weight}}{72,309}-\stackrel{\textit{first week}}{2810}-\stackrel{\textit{second week}}{1048}-\stackrel{\textit{third week}}{1048} \\\\\\ x=67403\implies x=67000+403\implies x=67Kgs~~ 403Grams[/tex]
