a) 70 - 5 (x - 3) = 45
5 (x - 3) =70-45
5 (x - 3) =25
(x - 3)=25:5
(x - 3)=5
x=5+3
x=8
b) 10 + 2.x = 4^5 : 4^3
10 + 2.x=4^2
10 + 2.x=16
2.x=16-10
2.x=6
x=6:2
x=3
c) 2x - 138 = 2^3 . 3^2
2x - 138 = 8.9
2x - 138 = 72
2x=72+138
2x=210
x=210:2
x=105
d) 231 - (x - 6) = 133 : 13
(đề sai)