Step-by-step explanation:
You can find d by subtracting a number by its precedent ⇒d=4−(−3)=7 or d=11−4=7 and so on! It's always going to be the same value. Another way to do this since it's "only" the 15th term is by hands or calculator. They already gave you the four terms, which will help you find the difference " d "
