20÷（2÷0.3）÷（3÷0.4）÷（4÷0.5）÷（5÷0.6）÷（6÷0.7）=20÷2×0.3÷3×0.4÷4×0.5÷5×0.6÷6×0.7=10×(0.3÷3)×(0.4÷4)×(0.5÷5)×(0.6×6)×0.7=10×0.1×0.1×0.1×0.1×0.7=0.001×0.7=0.0007...