Explaination
First, find the lowest common denominator for all four fractions.
In this case it is 40.
If you convert all four fractions to 40ths:
$9331_w108_h39.png$
$1532_w108_h38.png$
$7431_w108_h38.png$
$7437_w108_h39.png$.
Therefore the largest fraction is $8779_w9_h38.png$.