Câu 1.
$a) 18.7 + 65 : 13 - 11 = 126 + 5 - 11$
$= 131 - 11$
$=$ 120
$\text{b) 125 - [68 + 8($37-35)^{2}$] : 4 = 125 - [68 + 8. $2^{2}$] : 4}$ $= 125 - [68 + 8.4] : 4$
$= 125 - [68 + 32] : 4$
$= 125 - 100 : 4$
$= 125 - 25$
$=$ 100
Câu 2.
$a) 25 + 3(x - 8) = 106$
$3(x - 8) = 106 - 25$
$3(x - 8) = 81$
$x - 8 = 81 : 3$
$x - 8 =$ 27
$\text{b) 2($3^{2x + 1}$ - 1) + 16 = 500}$
$\text{2($3^{2x + 1}$ - 1) = 500 - 16}$
$\text{2($3^{2x + 1}$ - 1) = 484}$
$\text{$3^{2x + 1}$ - 1 = 484 : 2}$
$\text{$3^{2x + 1}$ - 1 = 242}$
$\text{$3^{2x + 1}$ = 242 + 1}$
$\text{$3^{2x + 1}$ = 243}$
$\text{$3^{2x + 1}$ = $3^{5}$}$
$\text{=> 2x + 1 = 5}$
$\text{2x = 5 - 1}$
$\text{2x = 4}$
$\text{x = 4 : 2}$
$x =$ 2
