b: =>5/x=5/2
hay x=2
c: =>-3/2=x/8
hay x=-12
d: =>21/-18=21/x
hay x=-18
a, x = \(\dfrac{14\left(n-10\right)}{4}=\dfrac{7\left(n-10\right)}{2}\)
b, \(-\dfrac{5}{x}=\dfrac{25}{-10}\Leftrightarrow\dfrac{-5}{x}=-\dfrac{5}{2}\Rightarrow x=2\)
c, \(-\dfrac{3}{2}=\dfrac{x}{8}\Rightarrow x=-12\)
d, \(-\dfrac{7}{6}=\dfrac{21}{x}\Rightarrow x=-18\)