Tìm x

\(\dfrac{x-2}{2018}=\dfrac{x-3}{2017}=\dfrac{x-4}{2016}=\dfrac{x-5}{2015}\)

Tìm x biết:

a )   x - 1 3 = 2 3

b) 60%x = 90

c) 2 3 x - 1 2 = - 1