**Solution:**
Assuming 6 legs for each insect, 17 insects will have 102 legs.

But, there are 122 − 102 = 20 extra legs.

It is important to note that spiders have 8 legs and flies have 6 legs. So, there are 2 extra legs per spider on the web.

Thus, the 20 extra legs belong to 10 spiders.

**Alternative Solution through Equations:**
Let

*s* be the number of spiders and

*f* be the number of flies. Then,

*s* +

*f* = 17; and

8

*s* + 6

*f* = 122.

On solving the above two equations, we get

8

*s* + 6 (17 −

*s*) = 122; or

2

*s* = 122 − (6 × 17).

Thus,

*s* = 10.

**Food for thought:**
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