Given a mango seller sells 70% of the total mangoes and still has 150 kg left with him.
That implies 30% of the mangoes is equal to 150 kgs.
Let the total mangoes be denoted by x.
Then, x is given as:
![\begin{gathered} (30)/(100)x=150 \\ x=(150*100)/(30) \\ x=500\operatorname{kg} \end{gathered}]()
Therefore, the total amount of mangoes is equal to 500 kgs.