Given sides are 5cm, 6cm, 3 cm

Now the sum of any two sides of a triangle must be greater than the third side.

1. 5 + 3 > 6 => 8 > 6

2. 5 + 6 > 3 => 11 > 3

3. 6+ 3 > 5 => 9 > 5

So, a triangle is possible with these sides.

Now, since all the sides are of different length. 

Hense it is a scalene triangle.