Help me with this one too.. tak reti lah
if its not clear, ask me about it.
thank you

c. $ 620

Step-by-step explanation:

Given,

Number of friends = 3,

Rent of apartment for a month = $ 650,

So, the total rent for 2 months ( First and last ) = 2 × 650 = $ 1300

Let x be the amount of security they paid,

⇒ Total money paid by them = 1300 + x,

According to the question,

They each paid $ 640,

⇒ Total money paid by them = 3 × 640 = $ 1920

⇒ 1300 + x = 1920

⇒ x = 1920 - 1300 = 620,

Hence, the amount of security deposit was $ 620.