8.1÷（4.3×2-0.4）=8.1÷（8.6-0.4）=8.1÷8.2=81/82
先算括号里的乘和减即原式=8.1/(8.6-0.4) =8.1/8.2 =81/82希望对你有用
4.3*2=8.68.6-0.4=8.28.1/8.2=0.987805
