+37157 First one: 2 pi is one complete revolution
6x = 2pi
x = pi/3 = 3.1415/3 = ~1.047 sec
Second one:
this is a cosine function with a multiplier in front of -11
the cos function USUALLY ranges from -1 to 1....the -11 makes it range from -11 to 11
BUT the wave is also shifted UP by 28 units so it ranges from 17 to 39
the first minimum (17) occurs when?
-11 cos (pix/48 - 5pi/12) + 28 = 17 subtract 28 from both sides and then divide by -11
cos(pix/48 - 5pi/12) = 1 arcos both sides
pix / 48 - 5pi/12 = 0
x = 20 minutes 8:00 + 20 mins = 8:20
You should be able to do similar for the first maximum.... 
