tìm x , biết

a, \(\frac{4}{x+5}=\frac{3}{x-4}\)

b.5-\(\frac{2}{x}=\frac{3}{-7}\)

c, \(\frac{x+5}{6}-4=\frac{5}{2}\)

d,8-\(\frac{7}{x+4}=\frac{5}{2}\)

e,\(\frac{x}{7}=\frac{-15}{14}\)

f,2-\((2x+3)=7\)

thực hiện phép tính

a, \(\frac{-5}{21}+\frac{2}{9}\)

b, \(\frac{-4}{21}-\frac{5}{12}\)

c,\(\frac{6}{-4}+\frac{1}{8}\)

d, \(\frac{-56}{77}-\frac{30}{66}\)

e,\(\frac{-3}{9}+\frac{5}{-3}\)