Tiffany put a $550 item on layaway by making a 15% down payment and agreeing to pay $20 a month. How many months sooner would she pay off the item if she increased her monthly payment to $80?

If she makes a down payment of 15% (it is $82.5), she will owe $467.50

if she keeps paying $20 a month, she will make 23 full payments (for a total of $460) and will have to make a last payment of $7.50 (so 24 payments in total)

If she pays $80 / month instead, she will make just 5 full payments (for a total of $400) and the 6th payment for $67.50.

That said, she will repay the full amount in 6 payments instead of 24, so it will be 18 months sooner ...

18 months or 4 times faster