Can someone please help I need help asap show work also

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?

If f(x)=-x^2+6x-1 and g(x)=3x^2-4x-1,find(f+g)(x)

Define multiplicative inverse. give an example of a number and its multiplicative inverse.