Which situation could be modeled by the function y = 400 (1 - 0.17) x?

Looking at the equation, this could model a situation in linear decay rate process. The variable y represents the amount left after time x. The original amount is 400 units. Then, the decay rate is 17%. It is called linear because the time is multiplied to the rate, not an exponent which would now make it exponential decay rate.