y/12 is an equivalent fraction to 1/4. to make the denominator 12, 4 has been multiplied by 3. if something is done to denominator the same should be done to the numerator, so we have to multiply 1 by 3 too, as shown below(hope u could understand it)
1/4=y/12
1/4 =y/12
×3
1/4 = y/12
×3
=1/4=3/12
so the answer is 3/12
hope it helps.
