Rough estimate: We expect the dosages to be around 700 mg and 1300 mg, based on similar thinking to Example 1 above.
Let the amount the first patient gets be d mg.
The second patient will get d − 660.
Together, the two dosages must be: d + (d − 660) = 2000
That is 2d − 660 = 2000
2d = 2660
d = 1330
And d − 660 = 1330 − 660 = 670
So the first patient gets 1330 mg and the second gets 670 mg.