[1] 18.9*178.178+0.49-17.8*189.189
=18.9*17.8*10.01+0.49-17.8*18.9*10.01
=0.49
[2] 3.42*76.3+76.3*5.76+9.18*23.7
=76.3*(3.42+5.76)+9.18*23.7
=76.3*9.18+9.18*23.7
=9.18*(76.3+23.7)=918
[3] 12.5*3.79+1.25*31.7+125*0.304
=12.5*3.79+12.5*3.17+12.5*3.04
=12.5*(3.79+3.17+3.04)
=125
[4] 11.4*1.7+9.1*1.7-5*1.7+4.5*1.7
=1.7*(11.4+9.1-5+4.5)
=34
[5] 6*13+4.8*18-1.2*37
=6*13+6*0.8*18-6*0.2*37
=6*(13+0.8*18-0.2*37)
=6*20
=120