解:设甲书架原有7x本友凳,乙神告备书架原游毁有4x本依题意,得7x-112:4x-112=5:47x-112/4x-112=5/4(7x-112/4x-112)*(4x-112)4=(5/4)*(4x-112)44(7x-112)=5(4x-112)28x-448=20x-5608x=-112x=-14解得:7x=-984x=-56好像不太对劲??!