已知b分之a=d分之c=3 求(1)b分之a+b的值;(2)d分之c+d的值.

a/b=3,a/b+1=4,(a+b)b=4;
c/d=3,c/d+1=4,(c+d)/d=4
a/b=3,a=3b,c/d=3,c=3d
(a+c)/(b+d)=(3b+3d)/(b+d)=3(b+d)/(b+d)=3