(a/b)/(c/d)=(a*d)/(b*c)
830 (1)((5/8)*(2/3))/(5/9)= ((5/4)*(1/3)/(5/9)= (5/12)/(5/9)=(5*9)/(12*5)= 3/4
830(2)((3/4)*(1/3))/(1/2)= (1/4)/(1/2)=(1*2)/(4*1)= 1/2
830(3)((7/15)*(3 3/4))/(2 5/8)= ((7/15)*(15/4)/(21/8)= (7/4)/(21/8)=(7*8)/(4*21)= 2/3
830(4)((5/12)*(4/5))/(2/9)= (1/3)/(2/9)=(1*9)/(3*2)= 3/2
831(1)3/(1-(1/2))= 3/(1/2)=(3*2)/(1*1)=6
831(2)(1-(1/4))/(1 1/2)=(3/4)/(3/2)=(3*2)/(4*3)=1/2
831(3)((2/3)+(1/4))/(1 5/6)= (11/12)/(11/6)=(11*6)/(12*11)=1/2
831(4)(8 1/3)/((8/9)-(1/3))=(25/3)/(5/9)=(25*9)/(3*5)=15