Peter R. answered 10/04/22
Experienced Instructor in Prealgebra, Algebra I and II, SAT/ACT Math.
The formula for the "less than" question would be the difference in the two rents as a percent of the new apartment's rent (the new apartment is the "base" for the calculation). $550/$950 x 100 to convert to a percent. Don't forget to round as required.
If it said the new apartment is what percent more than the basement apartment (the reverse), the calculation would be $550/$400.
For the second question, they're not asking for how much more or less than one apartment is from the other, just the straightforward comparison: $400/$950 x 100 and round.