In all of the sentences provided, "fui" translates to "I was" in English.
- "Fui al médico" means "I went to the doctor."
- "Fui a Madrid" means "I went to Madrid."
- "Fui estudiante" means "I was a student."
- "Fui ayer" means "I was yesterday."
However, the most straightforward translation as "I was" would be in the sentences "Fui estudiante" and "Fui ayer."