7th Grade Math... Please help me ASAP

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?

Could somebody me with this radical simplification?

Given: circle o, cd is diameter, chord ab || cd. arc ab = 74°, find arc ca.