3x+2x+80+3x= 1280

Solution: x= 150, so 2x=300 3x=450 80+x=530.

A: There are 450 A, 300 B and 530 C.

2. Let the passenger car speed be 3x and the freight car speed be 2x. Whole journey 12x. The driving time is t

(3x+2x)t= 12x, and the result is t= 12/5 (five twelfth).