Answer:
[tex]\left\{ \begin{array}{ll} 2d+4p=28 \\ d+p=9 \end{array}[/tex]
Step-by-step explanation:
We are letting d represent the number of drinks and p represent the number of pizza slices.
We know that each drink d costs $2. We also know that each pizza slice p costs $4. They spent a total of $28. Therefore:
[tex]2d+4p=28[/tex]
We also know that 9 items was purchased all together. So, the total number of drinks d and pizza slices p sum to 9:
[tex]d+p=9[/tex]
Therefore, our system of equations is: