Someone please help with 6 and 7

Which of the following of the following sets of side lengths could not form a triangle?

Ijust need to see how to do this. so you don’t have to answer all of them just a step by step explanation of one.

Anew shopping mall is gaining in popularity. every day since it opened, the number of shoppers is 5% more than the number of shoppers the day before. the total number of shoppers over the first 10 days is 1258 how many shoppers were on the first day?