Query about Question 4 from "PrepSwift Quant Tickbox Quiz #5 (Algebra Column 2)" [6481]?

GRE GRE Quant Problem Solving
1

https://prepswift.gregmat.com/quizzes/quiz/prepswift-quant-tickbox-quiz-5-algebra-column-2 (Question 4)

Why is the answer not “(D)The relationship cannot be determined from the information given.”?

2

Because quantity A is some fixed number