mary’s share is 2/3 of nell’s share.

for easy understanding:
circle numerator , arrow to marry
circle denominator , arrow to nell.

so mary has 2u
nell has 3u.

nell’s share is 1/2 of tory’s share.

circle and arrow ,

nell has 1 u
tory has 2u

x3 to each of them so that its easy to compare,

nell has 3 u , tory has 6u , mary remains same, mary has 2 u.

so question wants mary share over tory share

2/6 fraction
simplest form is 1/3.