How to interret formulas such as the Simple discount

Question

interpret  this formula emphasizing the situations where and when you will daily use it

t=A-P/Pr

Answer 1

If r=interest rate in unit time (e.g., years) and t=time and P is the original price or principal, the amount A after time t is:

A=P+Prt, so Prt=A-P, and t=(A-P)/Pr, where Prt is the simple interest gained after time t.