How do you find a slope of a line using only two points? ?

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?

Average acceleration: i have no idea how to do this.

What is fraction that is equivalent to 3/8