(4 13/18-3 7/9)*(1/2-4/17)
(4 13/18-3 7/9)×(1/2-4/17)=1/4 1)4 13/18-3 7/9=85/18-34/9=85/18-68/18=17/18 2)1/2-4/17=17/34-8/34=9/34 3)17/18×9/34=1×1/2×2=1/4