You can compare values of fractions by making the denominators of both fractions equal to each other. In order to do this, we need to figure out the Least Common Denominator for both fractions, and in this case, it's 14. 14 has both 7 and 2 as factors, so it works.
For the first fraction, 4/7, we need to think: What number, when multiplied to 7, will give us 14? That will be 2. So multiply both the numerator and demoninator of that fraction by 2.
(4 * 2)/(7 * 2) = 8/14
For the second fraction, 1/2, what number, when multiplied to 2, will give us 14? 7. So multiply both numerator and denominator by 7.
(1 * 7)/(2 * 7) = 7/14
Now let's compare both of the fractions: 8/14 and 7/14.
8/14, or 4/7, is bigger because the numerator is a larger number than the numerator in the second fraction, 7/14.
Therefore, 4/7 is greater than 1/2.