a) x - 1/2 = -3/4
x = -3/4 + 1/2
x = -3/4 + 2/4
x = -1/4
b) 2/7 . x = -1/6
x = -1/6 : 2/7
x = -1/6 . 7/2
x = -7/12
c) ( 3/7 . x + 1 ) : (-4 ) = -1/28
3/7 . x + 1 = -1/28 . (-4)
3/7 . x + 1 = 1/7
3/7 . x = 1/7 - 1
3/7 . x = 1/7 - 7/7
3/7 . x = -6/7
x = -6/7 : 3/7
x = -6/7 . 7/3
x = -2