Tìm x biết

a) 2/3 . x - 4/7 = 1/8
b) 2/7 - 8/9 . x = 2/3
c) -2/3 : ( 1/2 - 3x ) = 5/3
d) ( 2/3 - 0,5x ) : 2/3 = 3/4