cheap way to know, is make them both the same denominator, by simply multiplying one fraction top and bottom by the denominator of the other, so let's do so then,
[tex]\bf
\cfrac{3}{11}\cdot \cfrac{7}{7}\implies \boxed{\cfrac{21}{77}}\qquad \qquad \qquad \qquad \cfrac{2}{7}\cdot \cfrac{11}{11}\implies \boxed{\cfrac{22}{77}}[/tex]
so, surely you can see who's larger.
