What is the concentration of agcl in an aqueous solution that contains 1.2 x 10-3 gram of agcl in 800. grams of the solution? 1.2 ppm 1.5 ppm 7.2 ppm 9.6 ppm?

Concentration can be measured in ppm. ppm means parts mer million. In terms of mass , ppm units are mg/kg. 
concentration of AgCl solution is the mass of AgCl solute in mg per 1 kg of solution. 
mass of AgCl present = 1.2 x 10⁻³ kg = 1.2 mg
mass of solution = 800 g = 0.800 kg
the mass of AgCl in 0.800 kg of solution  = 1.2 mg
therefore mass of AgCl in 1 kg of solution = 1.2 mg / 0.800 kg x 1 kg = 1.5 mg
concentration of AgCl is 1.5 mg/kg
since mg/kg = ppm 
concentration of AgCl = 1.5 ppm
answer is 1.5 ppm