Solution: X+Y=50 (1)

6X+4Y=230 (2)

Substitution: X=50-Y changed from (1) to: 6 (50-y)+4y = 230 300-6y+4y = 230 2y = 300-230 = 70y = 35 (vehicle).

Replace Y=35 with X=50-Y, and X=50-35= 15 (vehicle).

A: Medium-sized cars are 65,438+05, and small cars are 35.