Please answer at least one. The "^" means the power like Example:2 to the power of 6

1)0.5^3+0.3^3

2)I thought of a number. My number multiplied by 7 is 6 bigger than 50. Find my number.

3)It takes three identical water pumps 8 hours to fill a pool. How long would it take four of the same pumps to fill the pool?