a. 3636 : (12x - 91) = 36
=> 12x - 91 = 3636 : 36
=> 12x - 91 = 101
=> 12x = 101 + 91
=> 12x = 192
=> x = 192 : 12
=> x = 16
b. (x : 23 + 45). 67 = 8911
=> x : 23 + 45 = 8911 : 67
=> x : 23 + 45 = 133
=> x : 23 = 133 - 45
=> x : 23 = 88
=> x = 88 . 23
=> x = 2024
c. (19x + 2.52) : 14 = (13 - 8)2 - 4
=> (19x + 2.25) : 14 = 52 - 4
=> (19x + 50) : 14 = 25 - 4
=> (19x + 50) : 14 = 21
=> 19x + 50 = 21. 14
=> 19x + 50 = 294
=> 19x = 294 - 50
=> 19x = 244
=> x = 244 : 19
=> x = 244/19 (Xem lại đề)
d. -12 .(x - 5) + 7.(3 - x) = 5
=> -12x + 60 + 21 - 7x = 5
=> -19x + 81 = 5
=> -19x = 5 - 81
=> -19x = -76
=> x = -76 : (-19)
=> x = 4