Solve for x : 3x < 5
3x < 5 ⇒ 3x - 5 < 0
(we cannot cross multiply with 'x' as 'x' can be negative or positive)
⇒ 3−5xx < 0
⇒ 5x−3x > 0
⇒ (x−35)(x−0) > 0
Sign scheme of above expression is shown below
⇒ x ∈ (−∞,0) U (35,∞)