c

chỉ  giúp e với e đang gấp ạ=(

                                                          Bài giải

a, \(\left(\frac{1}{6}+\frac{1}{10}+\frac{1}{15}\right)\text{ : }\left(\frac{1}{6}+\frac{1}{10}-\frac{1}{15}\right)=\left(\frac{5}{30}+\frac{3}{30}+\frac{2}{30}\right)\text{ : }\left(\frac{5}{30}+\frac{3}{30}-\frac{2}{30}\right)=\frac{1}{3}-\frac{1}{5}=\frac{2}{15}\)

b, \(\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{4}-\frac{1}{5}\right)\text{ : }\left(\frac{1}{4}-\frac{1}{5}\right)=\left(\frac{60}{120}-\frac{40}{120}+\frac{30}{120}-\frac{24}{120}\right)\text{ : }\left(\frac{5}{20}-\frac{4}{20}\right)=\frac{13}{60}\text{ : }\frac{1}{20}=\frac{13}{3}\)

Ta có : 

    a, \(\left(\frac{1}{6}+\frac{1}{10}+\frac{1}{15}\right)\text{ : }\left(\frac{1}{6}+\frac{1}{10}-\frac{1}{15}\right)=\left(\frac{5}{30}+\frac{3}{30}+\frac{2}{30}\right)\text{ : }\left(\frac{5}{30}+\frac{3}{30}-\frac{2}{30}\right)=\frac{1}{3}-\frac{1}{5}=\frac{2}{15}\)

b,

 \(\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{4}-\frac{1}{5}\right)\text{ : }\left(\frac{1}{4}-\frac{1}{5}\right)=\left(\frac{60}{120}-\frac{40}{120}+\frac{30}{120}-\frac{24}{120}\right)\text{ : }\left(\frac{5}{20}-\frac{4}{20}\right)=\frac{13}{60}\text{ : }\frac{1}{20}=\frac{13}{3}\)

m = 3125

thế số âm thì sao bạn bạn xem lại nhé

5/12 + 3/4 - 1/3 = 7/6 - 1/3 = 1/2

 1/4 - 3/7 + 11/14 = -5/28 + 11/14 = 17/28

a) \(\frac{5}{12}+\frac{3}{4}-\frac{1}{3}=\frac{5}{12}+\frac{9}{12}-\frac{4}{12}=\frac{5+9-4}{12}=\frac{10}{12}=\frac{5}{6}\)
b) \(\frac{1}{4}-\frac{3}{7}+\frac{11}{14}=\frac{7}{28}-\frac{12}{28}+\frac{22}{28}=\frac{7-12+22}{28}=\frac{17}{28}\)

chọn A

A là đáp án đúng

a x 5 + b x 2 + a x 3 + b x 6

= a x 5 + a x 3 + b x 2 + b x 6

= a x (5+3) + b x (2+6)

= a x 8 + b x 8

= 8 x (a+b)

thay a+b=1998

ta có biểu thức: 8 x 1998

                    = 15984

= 107/36

1/4+4/3+5/9+10/12

=9/36+48/36+20/36+30/36

=107/36