3.96-2.89+3.96+2.89
=3.96×2+(2.89-2.89)
=(4-0.04)×2+0
=4×2-0.04×2
=8-0.08
=7.92
5.82-2.27+3.18-0.73
=(5.82+3.18)-(2.27+0.73)
=9-3
=6