Percentages
Let's say the original price of the shirt was 100%.
It was marked down by 85%, thus the final value is 100% - 85% = 15%
$26 represents 15% of the original price, thus the original price can be computed as:
$26 / 15%
We cannot divide directly by a percentage, we must first convert it to decimal:
15% = 15 / 100 = 0.15
Now we calculate:
Original price = $26 / 0.15 = $173.33
The shirt's cost was originally $173.33