With fractions, you are allowed to multiply or divide the top and bottom of the fraction by some number, as long as you multiply (or divide) everything on the top and everything on the bottom by that number.
So 1/4 = 2/8 (multiplying top and bottom by 2).
in your example as above you need to make the 4 on the bottom of the fraction an 8. You can see that 4 x 2 is 8 so this will give you eighths. As you multiplied the bottom number by 2 you must also multiply the top number by 2, so 1 x 2 = 2. Hence 1/4 is 2/8 so you can see there are 2 eighths in one quarter.
This answer will help you out a lot more than my first one as you can now work out these problems for yourself, better than asking ABer's to do your homework for you! :-)