2. Painting walls in a new building 10 workers would complete in 15 days. However, at the beginning, there were only 6 workers, and after 5 days, 2 more workers joined, and after another 3 days, 4 more workers joined. In how many days was the job finally completed?
2. If 10 workers would complete the entire job in 15 days, then that job would be completed by 1 worker in $10 \cdot 15=150$ days, which means 1 worker would complete $\frac{1}{150}$ of the job in 1 day.

Then, 6 workers would complete $\frac{30}{150}$ of the job in 5 days.

2 POINTS

Similarly, 8 workers would complete $\frac{24}{150}$ of the job in 3 days.

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12 workers worked for $\mathrm{x}$ days and completed $1-\frac{30}{150}-\frac{24}{150}=\frac{96}{150}$ of the job.

2 POINTS

Thus, $12 \cdot \mathrm{x}=96$ so $\mathrm{x}=8$.

1 POINT

In the end, the entire job was completed in $5+3+x=16$ days.

2 POINTS