Step-by-step explanation:
1.)20x + 100 = 1440
-Let the number of couples be x. So, the total amount paid by all the couple’s are $20x. School paid $100 as security, so the total amount paid is
$ (20x + 100)
2.) 20x = 1440 - 100 ⇒ 20x = 1040
X = 52
3. ) The security money is $100, so the couples paid $1440- 100 = $1040 in total. As the couples paid $ 20 each than- = 52