PLS HELP !! Find the length of the third side. If necessary, round to the nearest tenth. ​

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?

Find the domain of the following expression: 1/(√x)-2

1.based of the diagrams what is the the value of x? 2.how would you verify your answer for x