(1-3/4)*(4/5 -3/4) 14*(1/2+1/3+1/4) 1/3*6/7-1/7*3/4
(1-3/4)•(4/5-3/4)=1/4•(16/20-15/20)=1/4•1/20=1/80. 14•(1/2+1/3+1/4)=14•(6/12+4/12+3/12)=14•13/12=7•13/6=91/6=15 1/6. 1/3•6/7-1/7•3/4=6/21•3/28=3/98.