1.=8.6*2/3+8.6*1/3
=8.6*（2/3+1/3)
=8.6*1=8.6
2.=2.74*二又五分之四+7.26*二又五分之四
=二又五分之四*（2.74+7.26）
=二又五分之四*10
=28
3.=9999*7778+(3333*3)*(6666/3)
=9999*7778+9999*2222
=9999*(7778+2222)
=9999*10000
=99990000
4.=5.6*69.32+6.932+69.32*4.3
=5.6*69.32+69.32*0.1+69.32*4.3
=69.32*(5.6+0.1+4.3)
=69.32*10
=693.2