Complex sentence: Lehrer's explanation of the two calculations is entirely correct, but presented at rapid speed, with minimal visual aids, and with snide remarks thrown in, making it difficult for most audience members to follow the otherwise simple calculations being performed.
Split into simpler sentences: Lehrer's explanation of the two calculations is entirely correct, but presented at rapid speed, with minimal visual aids, and with snide remarks thrown in. So it is difficult for most audience members to follow the otherwise simple calculations being performed.