Why does y equal 3 represent a function but x equal 3 is not?

The step function g(x) is defined as shown. what is the range of g(x)? ***answer choices in picture.

Jayne is studying urban planning and finds that her town is decreasing in population by 3% each year. the population of her town is changing by a constant rate. true or false?

The difference of two numbers is 40. find the numbers if 0.3 parts of one number is equal to 37.5% of the other one.