$\text{a. 16x + 40 = 10 . 3² + 5 (1 + 2 + 3)}$
$\text{16x + 40 = 10 . 9 + 5 . 6}$
$\text{16x + 40 = 90 + 30}$
$\text{16x + 40 = 120}$
$\text{16x = 80}$
$\text{x = 5}$
Vậy $\text{x = 5}$
$\text{b. 92 - 2x = 2 . 4² - 3 . 4 + 120 : 15}$
$\text{92 - 2x = 2 . 16 - 12 + 8}$
$\text{92 - 2x = 32 - 12 + 8}$
$\text{92 - 2x = 28}$
$\text{2x = 64}$
$\text{x = 32}$
Vậy $\text{x = 32}$
