The highest common factor of a and b is x. y is also a common factor of a and b if y is a number greater than x.
False
x is the greatest common factor for a and b. So, there can't be any other factor which is greater than x for a and b.
The given statement is false because it states that y is a common factor of a and b and also greater than x.
Example: HCF of 12 and 18 = 6. So there can't be any number greater than 6 which is a common factor to both the numbers 12 and 18.