In how many ways can 10 identical shirts and 7 identical trousers be placed in a row on a shelf so that two trousers may not be together ?

Explanation

To solve the problem of arranging 10 identical shirts and 7 identical trousers in a row on a shelf such that no two trousers are together, we can follow these steps:

### Step 1: Arrange the Shirts
First, we will arrange the 10 identical shirts. Since they are identical, there is only one way to arrange them. We can denote the shirts as 'S'.

Arrangement:
```
S S S S S S S S S S
...