DIM A!
DIM B!
DIM C!

A! = 561
B! = 633

C! = Gcd!(A!, B!)

PRINT  C!, " *", A! / C!, " =", A!
PRINT  C!, " *", B! / C!, " =", B!

FUNCTION Gcd! (X!, Y!)
  '--------------------- 
  'Using Euclid's Method 
  '--------------------- 
  LOCAL Z!
  Z! = 1
  WHILE Z! > 0
    Z! = MOD(X!, Y!)
    X! = Y!
    Y! = Z!
  WEND
  FUNCTION = X!
END FUNCTION

Result:

3 * 187 = 561
3 * 211 = 633