i don't get how to do this math question, even looking at the answer... (1/x)-b

You just want to simplify it I guess

 

\(\frac{(\frac{1}{x})-b}{x}\\ =[(\frac{1}{x})-b]\div \;x\\ =[\frac{1}{x}-b]\div \;x\\ =[\frac{1}{x}-\frac{bx}{x}]\div \;\frac{x}{1}\\ =[\frac{1-bx}{x}]\div \;\frac{x}{1}\\ =[\frac{1-bx}{x}]\times \;\frac{1}{x}\\ =\frac{1-bx}{x^2}\\ \)

 

Does that help  ?