Answer: Some solutions are:
1) Comí/Comimos
2) Vendí/Vendimos.
The actual right answer depends on the Subject of the sentences.
Explanation: We need to complete the sentences with the word in the parentheses.
1) (comer) muy bien en El Cráter.
Here the action is "comer" that means "eat", and we need to conjugate it in the "preterito perfecto" (means past) there are different ways to complete this sentence because we don't know about who is the sentence; this may be completed as:
"Comí muy bien en El Cráter"
"Comimos muy bien en El Cráter"
"Comieron muy bien en El Cráter"
etc
2) (vender) muchas camisetas allí.
Here the action is "vender", that means "sell", and the approach is the same as before, and we have the same problem as before, we don't know in what is the subject here, so we can complete the sentence as:
"Vendí muchas camisetas allí."
"Vendimos muchas camisetas allí."
etc.