$\text{a) x + 1234 + 3012 = 4724.}$
$\text{⇒ x + 4246 = 4724.}$
$\text{⇒ x = 4724 - 4246.}$
$\text{⇒ x = 478.}$
$\text{Vậy x = 478.}$
$\text{b) x ÷ 7 × 34 = 8704.}$
$\text{⇒ x ÷ 7 = 8704 ÷ 34.}$
$\text{⇒ x ÷ 7 = 256.}$
$\text{⇒ x = 256 × 7.}$
$\text{⇒ x = 1792.}$
$\text{Vậy x = 1792.}$
$\text{c) x - 61 + 75 = 548.}$
$\text{⇒ x - 61 = 548 - 75.}$
$\text{⇒ x - 61 = 473.}$
$\text{⇒ x = 473 + 61.}$
$\text{⇒ x = 534.}$
$\text{Vậy x = 534.}$
$\text{d) 38934 ÷ x × 4 = 84.}$
$\text{⇒ 38934 ÷ x = 84 ÷ 4.}$
$\text{⇒ 38934 ÷ x = 21.}$
$\text{⇒ x = 38934 ÷ 21.}$
$\text{⇒ x = 1854.}$
$\text{Vậy x = 1854.}$
