a.12x+19x-123=280
12x+19x =280+123
12x+19x =403
31x =403
x=403:31
x=13
b. 5-(17-3)=x-(2-15)
5-14 =x-(-13)
-9 =x+13
=> x=(-9)-13=-22
Tìm x:
a. 12x + 19x - 123 = 280
(12 + 19).x - 123 = 280
31.x - 123 = 280
31.x = 280 + 123
31.x = 403
x = 403 : 31
x = 13
b) 5 - (17 - 3) = x - (2 - 15)
5 - 14 = x - (-13)
(- 9) = x + 13
=> x = (-9) - 13 = -22
a)12x + 19x - 123= 280 12x +19x = 280 +123 12x + 19x = 403 31x=403 x =403:31 x=13