I need help with this please

What is the domain of the step function f(x)=[2x]-1?

Twice the sum of a number and 2 is equal to three times the difference of the number and 8. find the number.

Apopulation of 1500 insects grows exponentially, by a factor of 3 every week. select all equations that represent or approximate the population, p, as a function of time in days, t, since the time it was 1500.