Let the original price be x.
It was marked down by 25%, means it was reduced by 25%.
If it was reduced by 25%, it means its value is 100% - 25% = 75%
The price is now $3.15
75% of x = 3.15
(75/100)x = 3.15
0.75x = 3.15
x = 3.15/0.75
x = 4.2
The original price of the pair of mittens = $4.20.
I hope this helps.
