80.7*8.7+8.07*13=8.07*87+8.07*13=8.07*(87+13)=8.07*100=807
24分之17*5分之1+24分之7/5+5分之1
=17/120+7/120+1/5=24/120+1/5=1/5+1/5=2/5
3.3.63*1.3+3.46*9.7-3.46=3.63+3.63*0.3+3.46*10-3.46*0.3-3.46=(3.63-3.46)+34.6+(3.63-3.46)*0.3=0.17+34.6+0.17*0.3=34.77+0.051=34.821
4,0.45*6又25分之11+3.56/2又9分之2=9/20*91/25+89/25*1/(20/9)
=9/20*91/25+89*9/(25*20)=
=9*(91+89)/(20*25)=9*180/20*25=81/25=3又6/25
5,19.75-（1.75*13分之8+1又4分之3*13分之5）
=79/4-(7/4*8/13+7/4*5/13)
=79/4-7/4*/(8/13+5/13)
=79/4-7/4=72/4=18
6,17/51+（68分之1+51分之2）*17=17/51+17/68+24/51
=1/3+1/4+2/3)
=(4+3+8)/12
=15/12
=1又1/4
7,1.25*9.1*0.7+1025*9.1*0.1
=9.1*(1.25*0.7+1025*0.1)
=9.1*(1.25*0.7+(125-12.5))
=9.1*1.25*(0.7+100-10)
=9.1*1.25*90.7
=1031.7125
8,76*（23分之1-53分之1）+23*（53分之1+76分之1)-53*(23分之1-76分之1）
=76/23-76/53+23/53+23/76-53/23+53/76
=(76-53)/23-1-23/53+23/53+(23+53)/76
=1-1+1=1