Verified Answer :

First of all, to simplify a number/fraction, you must find a common multiple.
Both 12 and 42 is divisible by 6
\(\frac{12}{42}\)=\(\frac{2}{7}\) since 6 goes into 12, two times and goes into 42, 7 times. The answer is \(\frac{2}{7}\) when simplified. 

12/42 simplified are 2/7 because you divide them both by six which leads u to that  answer 
hope its helpful!!