Final answer:
The question pertains to mathematical concepts related to equations, direct and indirect proportionalities, and the representation of linear relationships, which are relevant to high school level mathematics.
Step-by-step explanation:
The student's question seems to reference concepts related to mathematical convenience, particularly concerning equations and their rearrangements into different formats for easier understanding or computation. This typically involves concepts like direct and indirect proportionalities, which are foundational in understanding relationships between different variables in mathematics. Additionally, the mention of 'straight-line' and 'in-advance' might hint at either algebraic methods such as the straight-line (linear) depreciation method in finance or the plotting of graphs to represent linear relationships. Both concepts are integral parts of high school mathematics curricula and involve analytical thinking to manipulate equations and understand their implications.
The phrase 'as the crow flies' is used to signify the shortest distance between two points, which is a straight line. This idea is akin to light traveling in a straight line and is often used in various geometrical contexts. Discussing a rubber sheet stretched taut and an ant walking in a straight line brings in imagery to describe the conceptual understanding of dimensions and the properties of space, which might be an allusion to physics, but is more likely here to illustrate the concept of a straight line in a geometrical sense.