.
Integer number 63 has the following decomposition into the product of prime numbers
    63 = 9*7 =  .        (1)
Integer number 84 has the following decomposition into the product of prime numbers
    84 = 12*7 =
.        (1)
Integer number 84 has the following decomposition into the product of prime numbers
    84 = 12*7 =  .      (2)
The LCM should have any of this prime numbers, 2, 3, and 7 in degrees what are maximal for each prime 
among these two decomposition (1) and (2).  
So      LCM(63,84) =
.      (2)
The LCM should have any of this prime numbers, 2, 3, and 7 in degrees what are maximal for each prime 
among these two decomposition (1) and (2).  
So      LCM(63,84) =  = 252.      ANSWER
 = 252.      ANSWER