5+1×10=? can someone explain the answer and operations ?

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?

Carrie started with 12 ounces of water when she begin to walk. when she was finish walking she had 2 1/4 ounces of water left. how much did she drank

Twelve less than a number is at most 20