Đáp án: $a)S=\{5\}$
$b)S=\{3\}$
Giải thích các bước giải:
$a)4(2x-3)=5x+3$
$⇔8x-12=5x+3$
$⇔8x-5x=3+12$
$⇔3x=15$
$⇔x=5$
`b)\frac{x-1}{6}+\frac{x+3}{2}=\frac{x+7}{3}`
`⇔\frac{x-1}{6}+\frac{3(x+3)}{6}=\frac{2(x+7)}{6}`
$⇔(x-1)+3(x+3)=2(x+7)$
$⇔x-1+3x+9=2x+14$
$⇔x+3x-2x=14-9+1$
$⇔2x=6$
$⇔x=3$