Решение:
Необходимо поставить глаголы в скобках в форму Past Simple.
- He found a wallet on the street yesterday. ('find' в Past Simple - 'found').
- We did not watch TV last night. ('do not watch' в Past Simple - 'did not watch').
- Did she write a letter to grandma? ('write' в Past Simple - 'wrote', в вопросе используется вспомогательный глагол 'did' и инфинитив).
- I ate too much cake at the party. ('eat' в Past Simple - 'ate').
- They built a sandcastle on the beach. ('build' в Past Simple - 'built').
Ответ: 1. found; 2. did not watch; 3. Did...write; 4. ate; 5. built.