Explanation:

- Initially, a camp of soldiers has food for 400 days, based on the total number of current soldiers.

- After 40 days, the situation changes. The number of soldiers becomes crucial to calculate the new duration the supplies will last.

- 150 soldiers leave after these 40 days, leaving fewer mouths to feed.

- With the reduced number of soldiers, the food then lasts for an extended period of 480 days.

- This change indicates that with fewer soldiers, the food lasts longer than initially planned.

We need to find how many soldiers were initially present:

- Let "S" be the initial number of soldiers.

- Initially, food for 400 days is for "S" soldiers.

- After 40 days, the food left is for 360 days for "S" soldiers.

- After 150 soldiers leave, the remaining soldiers are \(S - 150\).

- The food now lasts for 480 days for these remaining soldiers.

We set up the equation:

\(S \times 360 = (S - 150) \times 480\)

Solving for \(S\), we get 600.

So, the initial number of soldiers was 600.

- Option 2: 600

Therefore, .