I set up the equations x + y = 24 and x*y=-3468. Then I substituted for y and used the quadratic formula to come to two numbers rounded to about 72.1 and -48.1. Hope that helps :)
The beginning of the equation represents the length as the question states it is one less than twice the width. Because you need to multiply width and length to get area, you place the length equation and parentheses and multiply the answer to the equation by the width :) Hope this helps!
She is correct because they need to find how much is the discounted price, which is 3. So to see what percentage it is, they need to see how much 3 is worth in comparison to 15. If we spilt 15 into 5 parts to make every part worth 20%, the answer would be 3. Thus Arianna is correct.