6.3×1/2÷(1.8+2.7×1/2）
=6.3×1/2÷（1.8+1.35）
=3.15÷3.15
=1
0.56×（5/12-19/60+2.375）÷0.5
=0.56×（1/10+2.375）÷0.5
=0.56×2.475÷0.5
=1.386÷0.5
=2.772
（4/19×2.4+1.6×4/19）×4/5
=4/19×（2.4+1.6）×4/5
=4/19×4×4/5
=64/95