12.C
三
13.-30+25= -5
14.7/2+(-1/2)-(-1/3)+8/3
=6/2+9/3
=3+3
=6
15.先通分为
(16/24-6/24-9/24+5/24)x48
=6/24x48
=1/4x48
=12
16.
-18÷9+(-5/8)+15÷5
=-3-5/8+3
=-5/8
12.C
三
13.-30+25= -5
14.7/2+(-1/2)-(-1/3)+8/3
=6/2+9/3
=3+3
=6
15.先通分为
(16/24-6/24-9/24+5/24)x48
=6/24x48
=1/4x48
=12
16.
-18÷9+(-5/8)+15÷5
=-3-5/8+3
=-5/8