Answer :

[tex]\frac{9}{10}:\frac{2}{5}=\frac{9}{10}*\frac{5}{2}= \boxed{\frac{9}{4}}[/tex]
Dividing a fraction by a second fraction is the same as multiplying the first by the reciprocal of the second:
[tex] \frac{9}{10} / \frac{2}{5} [/tex]
= [tex] \frac{9}{10} * \frac{5}{2} [/tex]
= [tex] \frac{45}{20} [/tex]
= [tex] \frac{9}{4} [/tex]

Hope this helps! :)