Question

If a|30, then a|60
Demonstrate why this proof is wrong or give a counter-example:
Let a be a divisor of 60. Since a can only contain prime factors 2,3,5, and since all of these integers are factors of 30 as well, a|30

Answer 1

counterexample, 90 is divisible by 30, but not by 60

Answer 2

but 90 doesnt divide 30

Answer 3

got it guys