What is a sequence of numbers in which the difference between any two consecutive numbers is a constant called?

Using two or more complete sentences, describe how you can find a vector parallel to b=-2,3

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?

Can some one explain this i got sent this. is this a threat i’m scared