13/17×5/6+17/13÷6=13/17×5/6+17/13×1/6=13/17×(5/6+1/6)=17/13×1=17/131.8×3/4+1.2×3/4-3/4=(1.8+1.2-1)×3/4=2×3/4=3/2
13/17×5/6+17/13÷6 =(65/17+17/13)/6=(1134/17x13)/6=189/221(2)1.8×3/4+1.2×3/4-3/4=18x3/40 +12x3/40 -30/40=(54+36-30)/40=3/2