Answer :
so it went from 30 to 35, or 5 bucks, if we take 30 to be the 100%, what is 5 off of it in percentage?
[tex]\bf \begin{array}{ccll} amount&\%\\ \text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\ 30&100\\ 5&p \end{array}\implies \cfrac{30}{5}=\cfrac{100}{p}\implies p=\cfrac{5\cdot 100}{30}[/tex]
[tex]\bf \begin{array}{ccll} amount&\%\\ \text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\ 30&100\\ 5&p \end{array}\implies \cfrac{30}{5}=\cfrac{100}{p}\implies p=\cfrac{5\cdot 100}{30}[/tex]