a与b的比是5∶7,a是30,b是多少?4T*y-u-n6F-f8g1[7U'w
算式:提示1m(L2Z)b0w0|)z6R5b4T*y-u-n6F-f8g1[7U'w
答:b是8M._.[9b2s4F-?)I)[(\-i。4T*y-u-n6F-f8g1[7U'w