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
Well, check the picture below, that's a triangular prism
so.. if you notice, is really just 2 triangles and 3 rectangles stacked up to each other at the edges
so.. if you just find the area of the 3 rectangles, and the two triangles, sum all five areas up, and you're golden
in your picture, notice the tickmarks, that triangle has all sides equal to each other, so.. if one is 6 units, so are the other sides as well
now.. to get the area of a triangle is 1/2bh as you'd know... so.. what the dickens is the "h" or height of the triangle anyway, well

that's the altitude or height, you already know the base, notice the tickmark
so, get the area of those 2 triangles, and the 3 rectangles and sum them up, and that's the surface area of the triangular prism
The answer is 5/22,
first change the mixed fraction into an I'm proper fraction which will be 22/5
22/5×5/22=1
4(2y-9) is your answer factored completely out