(0.1-0.2+0.3)÷0.4÷0.5=1;
(0.1+0.2+0.3+0.4)÷0.5=2;
(0.1+0.2+0.3)÷(0.4x0.5)=3;
0.1÷(0.2+0.3)÷0.4x0.5=0.25.