Hi!
Samuel bought the mixer for $54,205. The value of this (the prive) decreases every year at a costant rate (so, for example, it may decrease of $100 every year).
we are solving for t and we should keep in mind that we multiply the price for the function (1 - rate/100)^time
in f(t) you put the value of year 1 for example

Solving for r will bring us to the solution, and we can substitute 1 to t since we are calculating how much it decreases after ONE year.
We would divide for 54205 to cancel out that 54205 multiplicating the parenthesis.
Also, the x is given by the formula (vale2-value1)/value1 to see how much the price changes from year 1 to year 2
We will get

Again, it would be:
f(t) = 54205(0.13)^1