i. 7√3 + √48 – √768
= 7√3 + √(16 × 3) – √(256 × 3)
= 7√3 + √16 × √3 – √256 × √3
= 7√3 + 4√3 – 16√3
= (7 + 4 – 16) √3
= –5√3
j. 9√5 – √125 + √720
= 9√5 – √(25 × 5) + √(144 × 5)
= 9√5 – √25 × √5 + √144 × √5
= 9√5 – 5√5 + 12√5
= (9 – 5 + 12) √5
= 16√5