Question

what kind of triangle is this?
equilateral
isosceles but not equilateral
scalene

Explanation:

An equilateral triangle has all three sides equal. An isosceles triangle has at least two sides equal. A scalene triangle has all sides of different lengths. In the given triangle, two sides are \(18\) (equal) and one side is \(15\) (different). So it meets the criteria of an isosceles triangle (two equal sides) but not an equilateral triangle (not all three sides equal).

Answer:

isosceles but not equilateral