YouIt wants the 20th number in the pattern.
AssistantThat’s it. What’s next?
YouLook at what I’m given and decide what fits the formulas I have.
AssistantRight. What did you decide?
YouIt goes up by 4 each time, so it’s arithmetic. First move is tn = a + (n−1)d.
AssistantOK. What’s the answer?
Youtn = a + (n−1)d … 5 + 19×4 = 81.
AssistantOK, go check it.
YouDone. Correct.