I need help i do not understand

Express the following as a function of a single angle. cos(60) cos(-20) - sin(60) sin(-20)

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

In a tutoring session, 2/3 of an hour was spent reviewing math problems. adelina attended 3/4 of the tutoring session. how much time did adelina spend at the tutoring session?