一道简算题!小妹在线等!急!

（78.6-0.786×25＋75％×21.4）÷15×1999
=[0.786*(100-25)＋75％×21.4]÷15×1999
=[78.6*75%+＋75％×21.4]÷15×1999
=75%*(78.6+21.4)÷15×1999
=75%*100÷15×1999
=75÷15×1999
=5*1999
=5*(2000-1)
=10000-5
=9995

（78.6-0.786×25＋75％×21.4）÷15×1999
=(78.6*1-78.6*0.25+75%*21.4)/15*1999
=[78.6*(1-0.25)+0.75*21.4]/15*1999
=[(78.6+21.4)*0.75]/15*1999
=75/15/*1999
=5*(2000-1)
=10000-5
=9995

(0.786*100-0.786*25+0.75*21.4）÷15×1999
=(0.786*75+0.75*21.4）÷15×1999
=[0.75(78.6+21.4)]÷15×1999
=75÷15×1999
=5*1999=5*2000-5=9995

（78.6-0.786×25＋75％×21.4）÷15×1999
={(78.6-78.6*25/100)+0.75*21.4}÷15×1999
＝（0.75*78.6+0.75*21.4)÷15×1999
=0.75*(78.6+21.4)÷15×1999
=0.75*100÷15×1999
＝0.05*100*1999
=5*1999
=5*(2000-1)
=10000-5
=9995