There could be many answers to this, but one of them is 2/424. Other answers could include 3/636, 4/848, or 5/10510. The way that you find equivalent fractions can be done one of two ways. You can either take the original fraction and put it into simplest form or make the fraction a value that could be taken into simplest form.
For example, your fraction, 1/212 is already in simplest form. Simplest form is when the numerator and the denominator cannot be decreased any lower. 2/424 can be taken into simplest form of 1/212. To find simplest form, you must look at the denominator and the numerator of your fraction and see if the have any common factors.The numbers 22 and 44 have a common multiple of 22. You would then divide both the numerator and the denominator by the number, in this case 22. This would give you 1/212.
In the case that you stated above, 1/212 is already in simplest form. Therefore, you cannot take it down. So, to find an equivalent fraction you will have to do the opposite of what we did above. You would multiply the numerator and the denominator by a number(it does not have to be a common factor. So, you could get anything from 2/424 to 250/500250500 and beyond.
I hoped this helped :) Leave a comment if you need help with anything else.