a)12. (x - 3) : 3 = 4^3 + 2^3
12 . (x - 3) : 3 = 64 + 8
12 . (x - 3) : 3 = 72
12 . (x - 3) = 72 . 3
12 . (x - 3) = 216
x - 3 = 216 : 12
x - 3 = 18
x = 18 + 3
x = 21
b) (20 + 5x) : 5^2= 5^4
(20 + 5x) : 25 = 625
20 + 5x = 625 . 25
20 + 5x = 15625
5x = 15625 - 20
5x = 15605
x = 15605 : 5
x = 3121
c) x + 5.2 - (2^5 - 16.3 : 6 - 15) = 0
x + 10 - (32 - 48 : 6 - 15) = 0
x + 10 - (32 - 8 - 15) = 0
x + 10 - 9 = 0
x + 1 = 0
x = 0 - 1
x = -1
d) 10 + 2 . x = 4^15 : 4^13
10 + 2 . x = 4^2
10 + 2 . x = 16
2 . x = 16 - 10
2 . x = 6
x = 6 : 2
x = 3
^ = mũ
$Xin hay nhất nhé!$