Babu and Aasha can do a job together in 7 days. Asha is $1\frac{3}{4}$times as efficient as Babu. The same job can be done by asha alone is 

If  babu can do job in x days, then asha can do the same job in $\frac{4x}{7}days$

$\therefore$They work together one day work  $=\frac{1}{x}+\frac{7}{4x}$

Also given (Asha and Babu)’ s one days job $=\frac{1}{7}$

$\therefore \frac{1}{x}+\frac{7}{4x}=\frac{1}{7}$

$\frac{4+7}{4x}=\frac{1}{7}\Rightarrow x=\frac{77}{4}$

$\therefore$Asha  alone can do the job in

$\frac{4}{7}\times \frac{77}{4}days=11days$