0.54/[(8.7+45.3)]*28.4

0.54/[(8.7+45.3)]*28.4
=0.54/54*28.4
=0.01*28.4
=0.284
15.32*4+4.68/0.25
=15.32*4+4.68*4
=（15.32+4.68）*4
=20*4
=80
3.9/(1.3*5)
=3.9/1.3/5
=3/5
=0.6