Im not sure if im correct can you help me with 6 and 7??

What is the value of the expression below? (81^2)^1/8

Pepe and leo deposits money into their savings account at the end of the month the table shows the account balances. if there pattern of savings continue and neither earns interest nor withdraw any of the money , how will the balance compare after a very long time ?

What is the similarity ratio of a cube with volume 729m^3 to a cube with volume 3375 m^3