3.2 adding and subtracting linear expression (continued) pg49

Which equation represents the partial sum of the geometric series?

Dylan and dusty plan to take weekly surfing lessons together. if the 2-hour lessons are $20 per person and they plan to spend $100 each on new surfboards, what is the maximum number of lessons the two can take if the total amount spent for lessons and surfboards is at most $480?

What are the first 4 terms in the multiplication pattern given by the formula 2×4n