Answer:
Option a. $300
Explanation:
Let
x ----> the cost of the rent monthly per person
we know that
The number of persons is 3 (Sal and two friends)
The cost of the security deposit per person is equal to

If Sal paid a total of $1,000 to move in
then
That means that the cost per person of two months of rent (first and last month) plus $400 (security deposit per person) must be equal to $1,000

solve for x
