Final answer:
To find the equation of the nth term, subtract the third term from the twentieth term to get the common difference. Then, use the formula for the nth term of an arithmetic sequence to find the equation of the nth term.
Step-by-step explanation:
To find the equation of the nth term, we need to first determine the common difference, which is the difference between any two consecutive terms. We can do this by subtracting the third term from the twentieth term: 83 - 15 = 68. Now, we can use the formula for the nth term of an arithmetic sequence:
an = a1 + (n - 1)d
where an is the nth term, a1 is the first term, n is the position of the term, and d is the common difference.
Substituting the known values, we get:
an = 15 + (n - 1)68
Simplifying, we have:
an = 68n - 53