数学大能救命

数学大能救命

(1)23+(-73) =-50.
(2)(-84)+(-49) =-133.
(3)7+(-2.04)=4.96.
(4)4.23+(-7.57) =-3.34.
(5)(-7/3)+(-7/6)=-21/6=-7/2.
(6)9/4+(-3/2)=3/4.
(7)3.75+(2.25)+5/4=6+1.25=7.25.
(8)-3.75+(+5/4)+(-1.5)=-5.25+1.25=-4.
(9)(-17/4)+(-10/3)+(+13/3)+(11/3)=-17/4+14/3=5/12.
(10)(-1.8)+(+0.2)+(-1.7)+(0.1)+(+1.8)+(+1.4)
=-3.5+3.5
=0.
(11)(+1.3)-(+17/7)=13/10-17/7=（91-170）/70=-79/70.
(12)(-2)-(+2/3)=-8/3.
(13)|(-7.2)-(-6.3)+(1.1)| =|-7.2+6.3+1.1|=0.2.
(14)|(-5/4)-(-3/4)|-|1-5/4-|-3/4|)题目有误
(15)(-2/199)*(-7/6-3/2+8/3)=-2/199*0=0.
(16)(4a)*(-3b)*(5c)*1/6=-10abc.
1. 3/7 × 49/9 - 4/3=7/3-4/3=1.
2. 8/9 × 15/36 + 1/27=10/27+1/27=11/27.
3. 12× 5/6 – 2/9 ×3
=10-2/3=28/3.
4. 8× 5/4 + 1/4
=10+0.25=10.25.
5. 6÷ 3/8 – 3/8 ÷6
=16-1/16=255/16.
6. 4/7 × 5/9 + 3/7 × 5/9
=(4×5+3×5)/(7×9)
=5/9.
7. 5/2 -（ 3/2 + 4/5 ）
=5/2-3/2-4/5
=1-4/5=1/5.
8. 7/8 + （ 1/8 + 1/9 ）
=7/8+1/8+1/9=10/9.
9. 9 × 5/6 + 5/6 =(9+1)×5/6=25/3.
10. 3/4 × 8/9 - 1/3
=2/3-1/3=1/3.
0.12χ＋1.8×0.9=7.2
0.12x=1.8×3.1，
x=15×3.1=46.5.
(9－5χ)×0.3=1.02
9-5x=3.4,
5.6=5x,
x=1.12.
6.4χ-χ=28+4.4
5.4x=32.4,
x=6.
11. 7 × 5/49 + 3/14 =5/7+3/14=23/14.
12. 6 ×（ 1/2 + 2/3 ）
=3+4=7.
13. 8 × 4/5 + 8 × 11/5
=8×(4/5+11/5)=8×3=24.
14. 31 × 5/6 – 5/6
=（31-1）×5/6=30×5/6=25.
15. 9/7 - （ 2/7 – 10/21 ）
=9/7-2/7+10/21
=1+10/21
=31/21.
16. 5/9 × 18 – 14 × 2/7
=10-4=6.
17. 4/5 × 25/16 + 2/3 × 3/4

=5/4+2/4=7/4.追问答案啊

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