\(\dfrac{\left(2x+1\right)}{3}=\dfrac{25}{9}\).\(\dfrac{3}{5}\)

1)8,65 + 281,35 - 26,75 - 13,25
2)(72,69 + 18,47) - (8,47 + 22,69)
3)2,07 - 7,64 - (-8,79) + 1,21 - 7,36
4)3,78 . ( 200 - 68) - 3,78 . (100 - 68)
5)3,4 . (23,6) - 3,4 . 445 + (-31,2) . 3,4
6)3,58 . 24,25 + 3,58 . 75,55

a)1/4 - (2x + 1/2)^2 = 0
b)1/2 x + 2/3 x - 1 = - 3 và 1/3
c)(x - 12)/4 = 1/2