Since all the three itens have the same price, we can use the same variable for all of them. In this case is the variable "p". The price of the purchase is 90, so the sum of all the itens should be equal to the total price as shown below:
[tex]\begin{gathered} p+p+p=90_{} \\ 3p=90 \\ p=\frac{90}{3}=30 \end{gathered}[/tex]The expression is 3p=90 and p = 30. The correct option is the third one.
