\(a,12-\left(4+105-13\right)+\left(4+105-3\right)\)

\(=12-4-105+13+4+105-3\)

\(=12+\left(-4+4\right)+\left(-105+105\right)+\left(13-3\right)\)

\(=12+0+0+10\)

\(=22\)

\(b,-15+\left(-17+21-35\right)+\left(4+105-13\right)\)

\(=-15-17+21-35+4+105-13\)

\(=\left(-15-35\right)+\left(-17-13\right)+\left(21+4+105\right)\)

\(=-50-30+130\)

\(=-50+100\)

\(=50\)

\(c,\left(\left|-5\right|+\left|+7\right|+\left|-9\right|\right)-\left(\left|+5\right|+\left|-7\right|+9\right)\)

\(=\left(5+7+9\right)-\left(5+7+9\right)\)

\(=0\)

a)   17/23+(1-17/23)

=17/23+1-17/23

=1

b)17/12+9/7-(2/7+5/12)

=17/12+9/7-2/7-5/12

=1+1

=2

c)

7/13-(4/7-6/13)

=7/13-4/7+6/13

=1-4/7

=3/7

a,17/23 + (1 - 17/23)

= 17/23 + 6/23

= 23/23 = 1

b,17/12 + 9/7 - (2/7 + 5 /12)

= (17/12 - 5/12) + (9/7 + 2/7)

= 1+1 = 2

c, 7/13 - ( 4/7 -6/13 )

= 7/13 - 4/7+ 6/13

= (7/13 + 6/13) -4/7

= 13/13 -4/7

= 1 -4/7 = 3/7

hok tốt✍️ ✍️

Lấy các số cùng mẫu gộp lại tính trước 

a) 17/23 + (1 - 17/23)

= 17/23 + 1 - 17/23

= (17/23 - 17/23)  + 1

= 0 + 1 = 1

b) 17/12 + 9/7 - (2/7 + 5/12)

= 17/12 + 9/7 - 2/7 - 5/12

= (17/12  - 5/12) + (9/7 - 2/7)

= 1 + 1 = 2

c) 7/13 - (4/7 - 6/13)

= 7/13 - 4/7 + 6/13

= (6/13 + 6/12) - 4/7

= 1 - 4/7 = 3/7

d) 7/18 + 3/16 + 11/18 + 13/16

= (7/18 + 11/18) + (3/16 + 13/16)

= 1 + 1 = 1

d) sửa 7/18 + 3/16 + 11/18 + 13/16

= (7/18 + 11/18) + (3/16 + 13/16)

= 1 + 1

= 2

a) \(\frac{7}{15}+\frac{9}{10}+\frac{8}{15}-\frac{-1}{10}-\frac{20}{10}+\frac{1}{157}\)

\(=\frac{7}{15}+\frac{9}{10}+\frac{8}{15}+\frac{1}{10}-\frac{20}{10}+\frac{1}{157}\)

\(=\left(\frac{7}{15}+\frac{8}{15}\right)+\left(\frac{9}{10}+\frac{1}{10}\right)-2+\frac{1}{157}\)

\(=1+1-2+\frac{1}{157}\)

\(=2-2+\frac{1}{157}\)

\(=0+\frac{1}{157}=\frac{1}{157}\)

b) \(\frac{1}{13}+\frac{16}{7}+\frac{3}{105}-\frac{9}{7}-\frac{-12}{13}\)

\(=\frac{1}{13}+\frac{16}{7}+\frac{1}{35}-\frac{9}{7}+\frac{12}{13}\)

\(=\left(\frac{1}{13}+\frac{12}{13}\right)+\left(\frac{16}{7}-\frac{9}{7}\right)+\frac{1}{35}\)

\(=1+1+\frac{1}{35}\)

\(=2+\frac{1}{35}\)

\(=\frac{70}{35}+\frac{1}{35}=\frac{71}{35}\)

Em nến gõ bằng công thức toán học em nhé. Như vậy mọi người nới hiểu đúng đề bài để trợ giúp cho em một cách tốt nhất em ạ!

1) \(\dfrac{5}{6}-\dfrac{6}{7}+\dfrac{7}{8}-\dfrac{8}{9}+\dfrac{10}{9}-\dfrac{5}{6}+\dfrac{6}{7}-\dfrac{7}{8}+\dfrac{8}{9}\)

\(=\left(\dfrac{5}{6}-\dfrac{5}{6}\right)-\left(\dfrac{6}{7}+\dfrac{6}{7}\right)+\left(\dfrac{7}{8}-\dfrac{7}{8}\right)-\left(\dfrac{8}{9}+\dfrac{8}{9}\right)+\dfrac{10}{9}\)

\(=0-0+0-0+\dfrac{10}{9}\)

\(=\dfrac{10}{9}\)

2) \(\dfrac{1}{13}+\dfrac{16}{7}+\dfrac{3}{105}-\dfrac{9}{7}-\dfrac{-12}{13}\)

\(=\left(\dfrac{1}{13}-\left(-\dfrac{12}{13}\right)\right)+\left(\dfrac{16}{7}-\dfrac{9}{7}\right)+\dfrac{3}{105}\)

\(=1+1+\dfrac{3}{105}\)

\(=\dfrac{213}{105}=\dfrac{71}{35}\)