(2.5-2.5×0.6)÷0.4=(2.5×(1-0.6))÷0.4=2.5×0.4÷0.4=2.5
=2.5x(1-0.6)÷0.4=2.5x0.4÷0.4=2.5
=2.5×(1-0.6)÷0.4=2.5×0.4÷0.4=2.5
2.5×(1-0.6)÷0.4=2.5