A.
To find a percentage of something, multiply by it's decimal. so 15% is 0.15
In c - 0.15c Louisa is taking the normal cost of a movie subscription and subtracting 15 percent of it off. hence the 15% discount.
We can rewrite this by skipping the subtraction part. If she's getting a 15% discount, you could say she is only paying 85% of it's normal price (100% - 15%). so put 85% in decimal and get 0.85c
Both expressions involve the same discount and both show that she is paying less than full price.
B.
They tell you the width is 16 feet. The length is 4% more than that. in other words the length is 104% the width. In decimal 100% is 1 and 4% is 0.04; 1 + 0.04 is 1.04.
1.04 * 16 = 16.64, which is the length.
Area (assuming the room is a rectangle) is length * width. so 16 * 16.64 whatever that equals is your area.