1.=5.7-4.2-8.4+10
=1.5-8.4+10
=11.5-8.4
=3.1
2.=-1/4+5/6+2/3-1/2
=-3/12+10/12+8/12-6/12
=7/12+8/12-6/12
=15/12-6/12
=9/12
=3/4
3.12-(-18)+(-7)+15
=12+18-7+15
=30-7+5
=23+5
=28
4.=4.7+8.9-7.5-6
=13.6-7.5-6
=6.1-6
=0.1
(1)—4.2+5.7—8.4+10 =5.7—4.2+10—8.4=1.5+1.6=3.1
3.1;
3/4;
28;
0.1
(……)
最终答案 1 3.1
2 3/4
3 28
4 0.1