5. (x+3)= 15
x + 3 = 3
x = 3 - 3
x = 0
20 + 5x= 5^5 : 5^3
20 +5x = 5^2
20 +5x = 25
5x= 25 - 20
5x = 5
x = 5 : 5
x = 1
5 2x- 3 - 2.5^2 = 5^2. 3
5 2x-3 - 2 . 25 = 5^2 . 3
5 2x - 3 - 2 . 25 = 25. 3
5 2x-3 - 50 = 25.3
5 2x-3 - 50 = 75
5 2x-3 = 75+50
5 2x-3 = 125
5 2x-3 = 5^3
2x - 3 = 3
2x = 3+3
2x = 6
x = 6:2
x = 3
--Chúc bạn học tốt! ^_^--
