15/8-4/7+2-3/7=15/8-(4/7+3/7)+2=15/8+1+2=15/8+3=39/8

Bài 2 

a.8/15+7/4+7/15+5/4

=8/15+7/15+7/4+5/4

=15/15+12/4

=1+3

=4

b.98,54-(41,82-35,72)

=98,54-6,1

=92,44

Bài 1 

a) 7/8 + 1 -  3/4 = 9/8

b) 15/4 - 3/8 - 1/6 = 5/6

\(\frac{11}{15}\cdot\frac{6}{7}+\frac{11}{15}\cdot\frac{8}{7}\) 

\(=\frac{11}{15}\cdot\left(\frac{6}{7}+\frac{8}{7}\right)\) 

\(=\frac{11}{15}\cdot2=\frac{22}{15}\)

Chú ý dấu "  \(\cdot\) " là dấu nhân

      11/15 x 6/7 + 11/15 x 8/7 

=    11/15 x (6/7 + 8/7)

=     11/15 x 2

=      22/15.

Mik ko chắc lắm nhé !

b, 98,54- (41,82 - 35,72 ) 

=98,54 - 6,1

=92,44

a.8/15+7/4+7/15+5/4

=8/15+7/15+7/4+5/4

=15/15+12/4

=1+3=4

b.98,54-(41,82-35,72)

=98,54-6,1

=92,44

Tham khảo nhé bạn :))

bbbbb

\(5\dfrac{3}{4}:3+2\dfrac{1}{4}\times\dfrac{1}{3}-\dfrac{1}{8}=\left(5\dfrac{3}{4}+2\dfrac{1}{4}\right)\times\dfrac{1}{3}-\dfrac{1}{8}\\ =8\times\dfrac{1}{3}-\dfrac{1}{8}=\dfrac{8}{3}-\dfrac{1}{8}=\dfrac{61}{24}\\ ----\\ \dfrac{3}{5}:\dfrac{5}{6}:\dfrac{6}{7}:\dfrac{7}{8}+\dfrac{2}{5}+\dfrac{23}{35}\\ =\dfrac{3}{5}\times\dfrac{6}{5}\times\dfrac{7}{6}\times\dfrac{8}{7}+\dfrac{2}{5}+\dfrac{23}{35}=\dfrac{18}{25}\times\dfrac{4}{3}+\dfrac{2}{5}+\dfrac{23}{35}=\dfrac{353}{175}\)

(2/7+5/7)+4/9=1+4/9=13/9

17/11+(7/15+5/11)=17/11+7/15+5/11=(17/11+5/11)+7/15=2+5/11=27/11

(19+1)+(18+2)+(17+3)+(16+4)+(15+5)+(14+6)+(13+7)+(12+8)+(11+9)+20)+10

=20+20+20+20+20+20+20+20+20+20=(20*10)+10

=210

1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20

=(1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+(10+20)

=20+20+20+20+20+20+20+20+20+30

=(20 x 9) + 30

=180 + 30

=210

tk nha