To find the percent tip Diego gave the server, we can set up an equation based on the relationship between the original dinner bill and the total amount paid, which includes the tip.
Let \( x \) be the tip percentage (in decimal form). The total amount paid can be expressed as the dinner bill plus the tip, which is calculated as the bill multiplied by \( x \):
\[ \text{Total Paid} = \text{Dinner Bill} + \text{Tip} \]
This can be rewritten as:
\[ 28.32 = 24 + 24 \cdot x \]
Rearranging gives us:
\[ 24 + 24\cdot x = 28.32 \]
So the correct equation to find the percent tip \( x \) is:
\[ \boxed{24 + 24 \cdot x = 28.32} \]