设甲乙两车的速度是5x和4x，A，B两地相距y千米

(4y/9)÷[5x*(1+20%)]=(5y/9-9.2)÷[4x*(1+30%)]

(4y/9)÷6x=(5y/9-9.2)÷5.2x

5.2*(4y/9)=6*(5y/9-9.2)

20.8y=30y-496.8

y=54