1, 3x + 2[ 5 - x ] = 0
3x + 10 - 2x = 0
3x - 2x = 0 - 10 = -10
x = -10
2, 3$x^{2}$ - 3x [ x - 2 ] = 36
3$x^{2}$ - 3$x^{2}$ + 6x = 36
6x = 36
x = 36 ÷ 6
x= 6
3,
[ x - 7 ][ x + 7] - $x^{2}$ + 5x = 6
$x^{2}$ - $7^{2}$ - $x^{2}$ + 5x = 6
49 + 5x = 6
49 + x = 6 ÷ 5
49 + x = $\frac{6}{5}$
x = $\frac{6}{5}$ - 49
x ≈ 49 , 8