$k) 5x + x = 39 – 3^{11}:3^9$
$ 6 x = 39 – 9$
$ 6x = 30$
$ x = 5$
$l) 7x – x = 5^{21} : 5^{19} + 3.2^2 - 7^0$
$6x = 25 + 3.4 -1$
$6x = 36$
$x = 6$
$m) 7x – 2x = 6^{17}: 6^{15} + 44 : 11$
$ 5x = 36 + 4$
$ 5x =40$
$ x =8$
$n) 0 : x = 0$
$ x = 0$
$o) 3^x = 9$
$ 3^x = 3^2$
$ x = 2$