The expression to represent the sale price, in dollars, of the dress is x - 0.3x dollars
Solution:
Given that dress that costs "x" dollars is on sale for 30% off
To find: expression to represent the sale price, in dollars, of the dress
Let the original price of dress is "x"
It is on sale for 30% offer. Which means 30 % of "x" is offer price
Sales price means the price of dress after offer
So the sales price is written as original price - offer price
Sales price = original price - offer price
Sales price = x - 30 % of x
On simplification we get,

Thus the sales price of dress is x - 0.3x dollars