`x/(25.27) + x/(27.29) + x/(29.31) + ... + x/(73.75) <= 2x - 149/75`
`⇔ 1/2 x (1/25 - 1/27 + 1/27 - 1/29 + 1/29 - 1/31 + ... + 1/73 - 1/75) <= 2x - 149/75`
`⇔ 1/2 x (1/25 - 1/75) <= 2x - 149/75`
`⇔ 1/2 x . 2/75 <= 2x - 149/75`
`⇔ x/75 <= 2x - 149/75`
`⇔ x <= 150x - 149`
`⇔ -149x <= -149`
`⇔ x >= 1`
`Vậy S = {x | x >= 1}`