$Câu 3:$
$a , x + 17 = 29$
$x = 29 - 17$
$x = 12$
$b , 4x + 235 = 411$
$4x = 411 − 235$
$4x = 176$
$x = 176 : 4$
$x = 44$
$c , 199 − 7(x − 35) = 52$
$7(x − 35) = 199 − 52$
$7(x − 35) = 147$
$x - 35 = 147 : 7$
$x - 35 = 21$
$x = 21 + 35$
$x = 56$
$d , 2x − 138 = 2^3 . 3^2$
$2x − 138 = 8 . 9$
$2x − 138 = 72$
$2x = 72 + 138$
$2x = 210$
$x = 210 : 2$
$x = 105$
