Table of values for f(x)=2x^2+6z-8

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

Cesar bought 7 items at the candy store. he bought candy bars for $0.50 each and packs of gum for $0.95 each. he spent a total of $6.80. what system represents the solution for the number of candy bars (x) and the number of pack gum (y) purchased?

Me get the answer and explain to me the steps to solve it would be greatly appreciated : )