[3*(42-x)+15]chia 5=24

Hướng dẫn trả lời:

$\text{[3.(42 - x) + 15] ÷ 5 = 24.}$

$\text{⇒ 3.(42 - x) + 15 = 24.5.}$

$\text{⇒ 3.(42 - x) + 15 = 120.}$

$\text{⇒ 3.(42 - x) = 120 - 15.}$

$\text{⇒ 3.(42 - x) = 105.}$

$\text{⇒ 42 - x = 105 ÷ 3.}$

$\text{⇒ 42 - x = 35.}$

$\text{⇒ x = 42 - 35.}$

$\text{⇒ x = 7.}$

$\text{Vậy x = 7.}$