Simplify the expression using sum or difference identities cos(12)cos(-3)-sin(12)sin(-3)

Two customers went to a post office. first customer paid $12 for 14 and 5 envelopes the second paid 24.80 for 10 postcards and 15 envelopes. what is cost of each envelope?

James was playing a game with his friends. he won 35 points. then he lost 15, lost 40 and won 55. how did he come out

Adolphin is swimming with her friend. the dolphin jumps to a height of 4.54.54, point, 5 meters above the surface of the water as her friend swims 9.89.89, point, 8 meters directly below her. what is the position of the dolphin's friend relative to the surface of the water? meters