Help, any answers that dont relate will get your account reported

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

Cody started biking to the park traveling 15 mph, after some time the bike got a flat so cody walked the rest of the way, traveling 4 mph. if the total trip to the park took 6 hours and it was 46 miles away, how long did cody travel at each speed? solve using rate times time= distance

1) prove that 731^3−631^3 is divisible by 100 2) prove that 99^3−74^3 is divisible by 25