Learn Spanish with a Joke - (#7)

The video tutorial explains a joke about a math notebook being sad due to having many problems. It covers the use of the verb 'estar' to express emotions in Spanish, the grammatical rule of combining nouns with 'de', and the importance of verb conjugation to indicate the subject. Additionally, it highlights exceptions in Spanish grammar, such as the word 'problema', which is masculine despite ending in 'a'.

Why is 'muchos problemas' used instead of 'mucho problema'?

What is the exception to the rule regarding the word 'problema'?