a) \(\dfrac{12}{16}\) = \(\dfrac{-x}{4}\) = \(\dfrac{21}{y}\) = \(\dfrac{z}{80}\) 

b) \(\dfrac{1}{3}\) x + \(\dfrac{2}{5}\)  ( x - 1 ) = 0

c) ( 2x - 3 )( 6 - 2x ) = 0

d) \(\dfrac{-2}{3}\) - \(\dfrac{1}{3}\) ( 2x - 5 ) = \(\dfrac{3}{2}\)

e) 2 |\(\dfrac{1}{2}\) x - \(\dfrac{1}{3}\) | - \(\dfrac{1}{4}\)