Toán Lớp 6: Tìm số nguyên x biết: a)123 -(x -4) = 38 b)20 -(-53 + x) = 72 c)360:[69-(13.x -5)]= 23.5

Question

Toán Lớp 6:  Tìm số nguyên x biết: a)123 -(x -4) = 38 b)20 -(-53 + x) = 72 c)360:[69-(13.x -5)]= 23.5

truongthanhhung · Answer

a)  123 -(x -4) = 38     123-x+4=38     123-x=38-4     123-x=34     x=123-34     x=89     b)     20-(-53+x)=72     20+53-x=72     53-x=72-20     53-x=52     x=53-52     x=1     c)360:[69-(13.x -5)]= 23.5     360:[69-(13.x -5)]=115     69-(13.x -5)=360:115     69-(13.x -5)=ko chia hết

kimlien · Answer

$ text{a, 123 - (x - 4) = 38}$   $ text{ 123 - x + 4 = 38 }$   $ text{ 127 - x = 38}$   $ text{    x  = 127 - 38}$   $ text{    x  = 89}$   $ text{Vậy x = 89}$   $ text{b, 20 - (-53 + x) = 72}$   $ text{ 20 + 53 - x = 72}$   $ text{ 73 - x =  72}$   $ text{  x  = 73 - 72}$   $ text{  x  =  1}$   $ text{Vậy x = 1}$   $ text{c,  360 : [69 - (13 . x -5)] = 23 . 5}$   $ text{   360 : [69 - 13.x + 5] = 115}$   $ text{   360 : [74 - 13x] = 115}$   $ text{   74 - 13x = 360 : 115}$   $ text{   74 - 13x = 3,13}$   $ text{   13x = 74 - 3,13}$   $ text{  13x = 70,87}$   $ text{ x = 70,87 : 13}$   $ text{ x = 5,452}$   $ text{Vậy x = 5,452}$