Sanjay gets fixed

Let the original salary be 'x' and yearly increment be 'y'

After 4 years, his salary was Rs. 4500

⇒ x + 4y = 4500

⇒ x = 4500 - 4y eq.[1]

After 10 years, his salary becomes 5400

⇒ x + 10y = 5400

⇒ 4500 - 4y + 10y = 5400

⇒ 6y = 900

⇒ y = 150

Putting this in eq.[1],

⇒ x = 4500 - 4(150)

⇒ x = 4500 - 600 = 3900

Hence, his original salary was Rs. 3900 and increment per year was 150 Rs.