Aparallelogram has side lengths of 9x+12 and 3x+7. what is the perimeter?

What are the values of each variable in the diagram below?

In a singing competition, there are 150 participants. at the end of each round, 40% of the participants are eliminated. how many participants are left after n rounds?

Travis and paula went to lunch.travis ordered a sandwich for $7.50 and paula ordered a burger for $5.25.after lunch,they left a 15% tip for the waiter.how many money did they spend altogether?