Let the length of the left arm of the balance be A and the length of the right arm be B, from which we can know that a≠b, and let the salesperson weigh the first and second medicines as X grams and Y grams respectively.

Bx = 50aay = 50b, …(6 points)? So x = 50aby = 50ba, …(8 points)

So x+y = 50ab+50ba ≥ 250ab? 50ba = 100, if and only if a=b, the equal sign holds ... (10)

Because a≠b, X+Y > 100, that is, the customer actually got more than 100 grams of drugs ... (12 points)