well, we'll first off put the point AC in component form by simply doing a subtraction of C - A, multiply that by the fraction 2/3, and that result will get added to point A, to get point B.
You would multiply 1.6kg by 1000 to get the amount of grams since 1000 grams equals one kilogram.
So 1.6x1000=1600
Then you would take 1600 and subtract 750 from it to get the difference which is 850g! Hope this helped :^)