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