If a problem is 30, the problem is the person who sits 30 cm from the computer screen. It is used to describe people that lack technical knowledge and can be used when you insult someone who's having computer problems.
Pros and cons are arguments for or against a particular issue. Pros are arguments which aim to promote the issue, while cons suggest points against it. The term has been in use since the 16th century and is a shortening of a Latin phrase, pro et contra, which means “for and against.” Considering the pros and cons of an issue is a very useful way to weigh the issue thoughtfully and reach an informed decision.