Final answer:
The given sentence "He wanted a new iPad, so he started mowing lawns to earn money" is a compound sentence, with two main clauses joined by the coordinating conjunction "so".
Step-by-step explanation:
The given sentence "He wanted a new iPad, so he started mowing lawns to earn money" is a compound sentence. A compound sentence contains two or more main clauses that are equally important to the meaning of the sentence. This sentence has two main clauses joined by the coordinating conjunction "so". Each main clause can stand alone as a sentence.