Answer:
Percentage markdown is 19.32% .
Explanation:
Formula

Where Change in value = |Final value - initial value|
As given
Hall's Discount Clothiers offered a particular brand of men's 3-piece suits for $79.95 last month.
Hall's has 150 suits remaining and decides to run a special weekend sale on these suits at $64.50 each
Final value = $64.50
Initial value = $79.95
Putting in the formula
Change in value = |64.50 - 79.95|
= |15.45|
= 15.45
Putting in the formula


Percentage change = 19.32%
Therefore the Percentage markdown is 19.32% .