Answer
The resonance structure should look like this:
Work Step by Step
1. Identify the pi bond next to the positive charge:
"Next" means that, there is exactly one bond between the pi bond and the atom with positive charge.
2. Draw the arrows:
Follow the same pattern we have learned in the chapter.
(Move the pi bond to the bond in the middle of they.)
3. Do the changes based on the arrows.
* Don't forget the formal charges!
4. Repeat these steps for the third ressonance structure.