Rules to follow:

Look at the two denominators (36 and 49).

Take their square roots. 
The larger one is one-half of the length of the major axis.
The smaller one is one-half of the length of the minor axis. 

Double those to find the lengths of the major or minor axes.

If the larger denominator is under the term in x, then
the ellipse looks like this: 

If the larger denominator is under the term in y, then
the ellipse looks like this: 


Edwin