What type of triangle is a 9.9 cm, 9 cm, 0.99 cm

It would be an isosceles triangle. Since there are two sides of the triangle that are congruent, it would be isosceles.

Isosceles has two congruent sides, scalene has none, and equilateral has three.  

(A good tip to do is this: count the number of syllables in each word. Then take away two. That's how many sides that triangle has.)

Ex: i-so-sce-les has four syllables. Take away two, you get two. Therefore, an isosceles triangle has two congruent sides.

Hope that helps!