a) 7(x-2) = 5 (3x+1)
⇔ 7x -14 = 15x +5
⇔ 7x -15x = 5 +14
⇔ -8x = 19
⇔ x = $\frac{-19}{8}$
Vậy S= { $\frac{-19}{8}$ }
b) x-3 = 18-5x
⇔ x +5x = 18 +3
⇔ 6x = 21
⇔ x = $\frac{7}{2}$
Vậy S= { $\frac{7}{2}$ }
c) $\frac{5x -4}{2}$ = $\frac{16x+1}{7}$
⇔ $\frac{7.(5x -4)}{14}$ = $\frac{2.(16x+1)}{14}$
⇔ 35x -28 = 32x +2
⇔ 35x -32x = 2 +28
⇔ 3x = 30
⇔ x = 10
Vậy S= {10}