If you are standing at the center of the cardinal points and you are facing north, what would the angles be if you turned the following ways: a) clockwise, now facing east
b) anticlockwise, now facing west

Expand by multiplying out:

14-15t + 36 = 1 -20t -1,
Because of the minus before the bracket, it changes the sign inside the bracket
-15t + 20t  = 1-1-14-36  Rearranging the ts on one side and the numbers on other
                                   side.
5t = -50  Divide both sides by 5.
t =  -50/5
t = -10.