So the formula for an arithmetic sequence (where you're adding or subtracting by the same number each time) is =
+ d(n - 1)
In this equation:
is the nth term
is the first term
d is the common difference (the number you're adding or subtracting each time)
n is the number of the term (e.g. 1st term, 2nd term, 3rd term etc)
So we're given that = -27, and we can find that d = 15 (because we add 15 each term). We just plug these values into the equation to get...
= -27 + 15 (n - 1)
It looks like that's your answer, D. But if you needed to solve it out further, you could:
We can use the distributive property...
= -27 + 15n - 15
Then combine like terms...
= 15n - 42
Hope that helps! Feel free to message me if you need clarification