Đáp án:
Bài 11 :
a) 15 : ( x + 2) = 3 b) 20 : ( 1 + x ) = 2
x + 2 = 15 : 3 1 + x = 20 : 2
x + 2 = 5 1 + x = 10
x = 5 - 2 x = 10 - 1
x = 3 x = 9
c)240 : ( x - 5) = 2² . 5² - 20 d) 96 - 3 . ( x + 1) = 42
240 : ( x - 5) = 4 . 25 - 20 3 . ( x + 1 ) = 96 - 42
240 : ( x - 5) = 100 - 20 3 . ( x + 1 ) = 54
240 : ( x - 5) = 80 x + 1 = 54 : 3
x - 5 = 240 : 80 x + 1 = 18
x - 5 = 3 x = 18 - 1
x = 3 + 5 x = 17
x = 8
e)5 . ( x + 35 ) = 515 f) 12 . x - 33 = 3² . 3³
x + 35 = 515 : 5 12 . x - 33 = 9 . 27
x + 35 = 103 12 . x - 33 = 243
x = 103 - 35 12 . x = 243 + 33
x = 68 12 . x = 276
x = 276 : 12
x = 23
g) 541 + ( 218 - x ) = 73 h) 1230 : 3 . ( x - 20 ) = 10
218 - x = 73 - 541 3 . ( x - 20 ) = 1230 : 10
218 - x = -468 3 . (x - 20 ) = 123
x = 218 - ( -468) x - 20 = 123 : 3
x = 686 x - 20 = 41
x = 41 + 20
x = 61
