Identify the type of sentence. we're going out for pizza; then we'll go to jerry's house to study. simple sentence compound sentence complex sentence compound-complex

This is a compound sentence.
A compound sentence contains at least two independent clauses, which is the case here. 
Independent clause no. 1: We're going out for pizza.
Independent clause no. 2: Then we'll go to Jerry's house to study.
A simple sentence would contain only one independent clause; a complex sentence would contain at least one dependent clause and one independent clause; a compound-complex sentence would contain at least two independent and dependent clauses.