Answer:
After julia rode her bike three blocks, the tire went flat.
Step-by-step explanation:
When past events are being told, all verbs in the sentence must be in the past tense.
The sentence is telling a fact that happened in the past, the verb ride is in the past, so the verb go must go in the past as well.
In this way the correct sentence is: after julia rode her bike three blocks, the tire went flat.