What is the volume of a spherical shell with inner radius 7 and outer radius 8?

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 soultion(s) to the quadratic equation 40- x^2=0

What are “like terms”? why can we only add like terms?