\(a,x-\frac{3}{4}=\frac{1}{7}\)

\(x=\frac{1}{7}+\frac{3}{4}=\frac{25}{28}\)

\(b,\frac{15}{x}-\frac{1}{3}=\frac{28}{51}\)

\(\frac{15}{x}=\frac{28}{51}-\frac{1}{3}=\frac{15}{17}\)

\(\Rightarrow x=17\)

học tốt ~~~

\(x-\frac{3}{4}=\frac{1}{7}\)

\(x\)          \(=\frac{1}{7}+\frac{3}{4}\)

\(x\)          \(=\frac{4}{28}+\frac{21}{28}\)

\(x\)           \(=\frac{4+21}{28}\)

\(x\)             \(=\frac{25}{28}\)

a) x - 3/4 = 1/7

x = 1/7 + 3/4

x = 25/28

b) 15/x - 1/3 = 28/51

15/x = 28/51 + 1/3

15/x = 45/51

x = 15.51/45

x = 17

a: \(=-25\cdot4-27=-100-27=-127\)

b: \(=-65:\left(-13\right)-25\cdot4=5-100=-95\)

c: \(=100\cdot\left(-47\right)+53\cdot\left(-100\right)=100\cdot\left(-100\right)=-10000\)

d: \(=\left[\left(-3\right)^{13}:3^{10}-73\right]:\left(-5\right)^2-14\)

\(=\left(-100\right):25-14=-4-14=-18\)

\(a,\dfrac{-3}{5}:\dfrac{15}{18}=\dfrac{-3}{5}\times\dfrac{18}{15}=\dfrac{-3}{5}\times\dfrac{6}{5}=\dfrac{-18}{25}\\ b,\dfrac{-5}{1}:\left(-4\right)=\left(-5\right):\left(-4\right)=\dfrac{5}{4}\\ c,-28:\dfrac{-7}{25}=-28\times\dfrac{25}{-7}=100\\ d,\dfrac{51}{8}:\dfrac{-2}{10}=\dfrac{51}{8}\times\dfrac{10}{-2}=\dfrac{51}{8}\times\left(-5\right)=\dfrac{-255}{8}\)

\(a)-3/5*18/15=-18/25\)

\(b)-5*1/-4=5/4\)

\(c)-28*25/-7=-100\)

\(d)51/8*10/-2=-255/8\)

A)  7/38 x 9/11 +7/38 x 4/11 -7/38 x 2/11

=7/38.(9/11+4/11-2/11)

=7/38

B) 5/31 x 21/25 + 5/31 x -7/10 - 5/31 x 9/20

=5/31.(21/25-7/10-9/20)

=5/31.(-31/100)

=-1/20

\(a.\)

\(\dfrac{17}{8}:\left(\dfrac{27}{8}+\dfrac{11}{2}\right)\)

\(=\dfrac{17}{8}:\left(\dfrac{27+44}{8}\right)=\dfrac{17}{8}:\dfrac{71}{8}=\dfrac{17}{8}\cdot\dfrac{8}{71}=\dfrac{17}{71}\)

\(b.\)

\(\dfrac{28}{15}\cdot\dfrac{1}{4^2}\cdot3+\left(\dfrac{8}{15}-\dfrac{69}{60}\cdot\dfrac{5}{23}\right):\dfrac{51}{54}\)

\(=\dfrac{28}{15}\cdot\dfrac{1}{4^2}\cdot3+\left(\dfrac{8}{15}-\dfrac{1}{4}\right):\dfrac{51}{54}\)

\(=\dfrac{28}{15}\cdot\dfrac{1}{4^2}\cdot3+\left(\dfrac{8\cdot4-15}{60}\right):\dfrac{51}{54}\)

\(=\dfrac{28}{15}\cdot\dfrac{1}{4^2}\cdot3+\dfrac{17}{60}:\dfrac{51}{54}\)

\(=\dfrac{28}{15}\cdot\dfrac{1}{16}\cdot3+\dfrac{17}{60}\cdot\dfrac{54}{51}\)

\(=\dfrac{7}{20}+\dfrac{3}{10}\)

\(=\dfrac{7+3\cdot2}{20}=\dfrac{13}{20}\)

Sai kìa phải bằng 11/20

\(a,\dfrac{1}{7}+\dfrac{1}{3}=\dfrac{3}{21}+\dfrac{7}{21}=\dfrac{10}{21}\\ b,\dfrac{-2}{3}+\dfrac{-5}{7}=\dfrac{-14+\left(-15\right)}{21}=\dfrac{-29}{21}\\ c,\dfrac{1}{2}-\dfrac{-1}{2}-\dfrac{1}{3}=\dfrac{3+3-2}{6}=\dfrac{4}{6}=\dfrac{2}{3}\)

\(a.\dfrac{4}{28}+\dfrac{12}{36}=\dfrac{1}{7}+\dfrac{1}{3}=\dfrac{3}{21}+\dfrac{7}{21}=\dfrac{10}{21}\\ b.\dfrac{-12}{18}+\dfrac{-15}{21}=\dfrac{-2}{3}+\dfrac{-5}{7}=\dfrac{-14}{21}+\dfrac{-15}{21}=\dfrac{-29}{21}\\ c.\dfrac{14}{28}+\dfrac{16}{32}-\dfrac{17}{51}=\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{17}{51}=1-\dfrac{17}{51}=\dfrac{2}{3}\)