A's sales are: (19/2) * (11/2) = 209/4 yuan.

B's sales are: 12*(49/6)=98 yuan.

C's sales are:15 * (31/3) =155 yuan.

So the sum of total sales is: A+B+C= 122 1/4.

(2)

The sum of sales of A and B is: A+B.

The percentage of sales is: (A+B)/(A+B+C)

Namely: (209/4+98)/(1221/4) = 49% (approximately)