a, x*3,6=-2*2,7
x*18/5=-27/5
x = -27/5 : 18/5
x = -27/5 *5/18
x = -3/2
b, |x - 0.25| - 5/6 = 1 2/3
|x - 0.25| - 5/6 = 5/3
|x - 0.25| = 5/3 - 5/6
|x - 1/4| = 5/6
th1. x- 1/4 = 5/6
x = 5/6 + 1/4
x = 13/12
th2. x - 1/4 = -5/6
x = -5/6 + 1/4
x = -7/12
vậy x thuộc {13/12; -7/12}