用简便方法计算。⑴5.85+1.89+2.15⑵24.8+14.6+15.4⑶42.5﹣22.17﹣7.83⑷3.8+1.37+6.2+12.63
10+3= 10+6= 9+10= 5+10= 7+10= 10+8=
10+2= 10+3=10+5= 3+10= 4+10= 6+10=
7-0= 6-1= 7-3= 8-5= 4-2= 9-7=
5+0= 10-2= 5-2= 7-3= 6-4= 8-4=
10-6= 8-6= 8-5= 8-3= 5-4= 5-1=