13.225. A certain order takes 3.6 hours longer to complete in workshop No.1 compared to workshop No.2, and 10 hours longer compared to workshop No.3. If under the same conditions, workshops No.1 and No.2 combine to complete the order, the completion time will be the same as in workshop No.3 alone. By how many hours more or less than one seven-hour workday does the completion of the specified order in workshop No.3 take?
## Solution.

Let $x$ hours be the time to complete the order in Workshop No.3. Then in the 1st workshop, this time is $x+10$ hours, and in the 2nd workshop, it is $-x+6.4$ hours.

$$
\text { According to the condition } \frac{1}{x+10}+\frac{1}{x+6.4}=\frac{1}{x} \text {, from which } x=8 \text { hours. }
$$

This means that the completion of the order in Workshop No.3 takes 1 hour longer than the 7-hour workday.

Answer: longer by 1 hour.