Find the area of these triangles

To complete your spring schedule, you must add calculus and physics. at 9: 30, there are three calculus sections and two physics sections; while at 11: 30, there are two calculus sections and three physics sections. how many ways can you complete your schedule if your only open periods are 9: 30 and 11: 30?

I’m stuck on this equation, anyone got the answer?

Determine which postulate or theorem can be used to prove that lmn =nmo