Can someone please help me

Rewrite the following without an exponent. (5/8)-1

In simplified exponential notation, the expression a^2•a^-3•a 1/a 0

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?