What is the lcm of 6 ,21 and 28 on?

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?

Which value would be a solution for x in the inequality 47-4x< 7

Check all that apply. f is a function. f is a one-to-one function. c is a function. c is a one-to-one function.