CAT 2019 Shift 2 Paper

Let the work be of 40 units
Amount of work done by Anil in one day $=\frac{40}{20}=2$ units
Amount of work done by Sunil in one day $=\frac{20}{20}=1$ units
Bimal does $10\%$ work i.e. 4 units.
Rest $40-4=36$ units is done by Anil and Sunil.
Let Anil took $\mathit{x}$ days. Therefore, Sunil took $\left(\mathit{x}-3\right)$ days. Therefore,
$2\times \mathit{x}+1\times \left(\mathit{x}-3\right)=36$
Or $\mathit{x}=13$ days.