**Solution:**
Assuming 6 legs for each insect, 12 insects will have 72 legs.

But, there are 78 − 72 = 6 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 6 extra legs belong to 3 spiders.

**Alternative Solution through Equations:**
Let

*s* be the number of spiders and

*f* be the number of flies. Then,

*s* +

*f* = 12; and

8

*s* + 6

*f* = 78.

On solving the above two equations, we get

8

*s* + 6 (12 −

*s*) = 78; or

2

*s* = 78 − (6 × 12).

Thus,

*s* = 3.

**Food for thought:**
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