1、4.25/5+2.5*0.2+5.25*0.2
=(4.25+2.5+5.25)*0.2
=12*0.2
=2.4
2、10/3/4+7*0.25+25/3*0.25
=(10/3+7+25/3)*1/4
=56/3*1/4
=14/3
3、2.5/(5/3)+5.25*0.6+0.6*(9/4)
=(2.5+5.25+2.25)*0.6
=10*0.6
=6
4、(2+1/3)*(6.75-2-5/6)-(11/12)/(3/7)
=7/3*3又11/12-11/12*7/3
=7/3*(3又11/12-11/12)
=7/3*3
=7