To create a function that starts at 20 and triples every 7, one can utilize the concept of exponential functions. The conditions can be expressed mathematically as f(0)=20 and f(7x)=2f(x). By taking the derivative of the second condition and substituting it into the first, a first-order differential equation is derived, leading to an exponential function solution. Applying the boundary condition from the first equation will yield the desired function. This approach effectively combines calculus with exponential growth principles.