(1)6.2-0.54÷1.8×5 =6.2-1.5,=4.7;(2)3.6×0.81+0.36×1.9 =3.6×0.81+3.6×0.19,=(0.81+0.19)×3.6,=3.6;(3)27.6-11.31-5.69=27.6-(11.31+5.69),=27.6-17,=10.6;(4)4.05÷[1.8×(3.36-2.86)]=4.05÷[1.8×0.5],=4.05÷0.9,=4.5.