Answer:
Selling price of a dozen brownies was $6 and markdown is $4.50.
Explanation:
Florence Price's Brownies and More markdown all brownies by 75%.
New selling price of brownies after markdown becomes $1.5 of a dozen.
As we know markdown of price = New selling price - Old selling price
Let the selling price of the brownies were x before markdown.
Then markdown of the selling price will be = 0.75x
Now we will put values in the the given formula
0.75x = x - 1.5
x - 0.75x = 1.5 ⇒ .25x = 1.5

So the selling price of a dozen brownies was = $6
and markdown of a dozen = 75% of $6 = 6×0.75 = $4.5