234*12.1+235*42.2-135*54.3
=(235-1)*12.1+235*42.2-135*54.3
=235*12.1-12.1+235*42.2-135*54.3
=(235*12.1+235*42.2)-135*54.3-12.1
=235*(12.1+42.2)-135*54.3-12.1
=235*54.3-135*54.3-12.1
=(235-135)*54.3-12.1
=100**54.3-12.1
=5430-12.1
=5417.9
235*12.1+235*42.2-135*54.3
=235*（12.1+42.2）-135*54.3
=54.3*（235-135）
=5430
我是最先作答的哦,不明白欢迎追问.