Formulas for AC Synchronous motors
S = f x 120 / N

Where:


S = Synchronous speed in RPM 
f = frequency in Hz
N = number of motor poles
120 = a mathematical constant


% Slip = (S - Full load RPM / S) x 100

Use those two formulae to solve all of the above.

By the way, your thread title says "synchronous motors", which would not be inclusive of "slip".