9/10×34.6+111×1.8+54.3÷10/9
　　=0.9×34.6+111×2×0.9+54.3×0.9
　　=0.9×(34.6+222+54.3)
　　=(1-0.1)×310.9
　　=1×310.9-0.1×310.9
　　=310.9-31.09
　　=279.81