2. They are equivalent, because they are like terms.
3. They are equivalent because when you add b 5 times, you are multiplying b by 5.
4. They are equivalent because when you multiply 4 by x you get 4x, then multiply 4x by x which gives you 4x² Since you multiplying x by x you square x.
5. They are not equivalent because c is being added 3 times which would give you 3c then you are adding it to 7. therefore it is not equivalent