Tom had the following scores on math tests: 91, 95, 87 and 83. He has one more test this marking period. What is the lowest grade he can receive if he hopes to raise his average above 90?

Can someone explain the elimination method to me for this problem?

In the diagram, the measure of angle 9 is 85° which angle must also measure 85°?

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?