Answer: Hello mate!
here we have the sum 30 + 42, and we want to factor the greatest common factor between 30 and 42.
We can try to go one for one, the biggest divisor of 30 is 15 (15*2 = 30), and 15 is not a divisor of 42, so this is not a common divisor of 30 and 42.
The second biggest divisor of 30 is 10 (10*3 = 30), and 10 is not a divisor of 42, so it is not a common divisor of 30 and 42.
the third biggest divisor of 30 is 6, (6*5 = 30) and 6 is a divisor of 42 (6*7 = 42)
then 6 is the biggest common factor of both 30 and 42
Now we can factor the sum as:
30 + 42 = 6*5 + 6*7 = 6*(5 + 7) = 6*12