Answer:

Step-by-step explanation:
The formula for nth term of a the sequence is given as 
<u>Finding the 10th term means finding
, which means to plug in 10 into n, in the nth term formula.</u>

To find the average you add all three numbers together and then divide by three since you added three.
$38,750.00 + $42,500.00 + $42,500.00 = $123,750.00
$123,750.00 ÷ 3 = $41,250
So your answer is $41,250
Constant: A value that doesn't change. Instead, it's a fixed value.
Variable: A symbol (usually a letter) standing in for an unknown numerical value in an equation.
Term: Either a single number or variable, or numbers and variables multiplied together. (Terms are separated by + or − signs, or sometimes by divide.)
Like Terms: Terms whose variables (and their exponents such as the 2 in x2) are the same. In other words, terms that are "like" each other.
Coefficient: A number used to multiply a variable.
You are adding s^2 to your 128 ft^2. s^2 is a common representation of a square. So you could think of it as adding an area of a square of side "s" to your deck.
So one way of drawing it is to draw a rectangle with area 128 ft^2 and attaching a square to one of its side. The square that is attached has a side lenght of "s."