Question

classify the triangles by side length. equilateral, isosceles, or scalene.

Explanation:

Step1: Recall triangle - side - length classification rules

An equilateral triangle has all sides equal, an isosceles triangle has at least two sides equal, and a scalene triangle has all sides of different lengths.

Step2: Analyze the first triangle

The side - lengths are 18, 21, 23. Since all side - lengths are different, it is a scalene triangle.

Step3: Analyze the second triangle

The side - lengths are 18, 20, 25. Since all side - lengths are different, it is a scalene triangle.

Step4: Analyze the third triangle

The side - lengths are 18, 25, 25. Since two sides have the same length (25), it is an isosceles triangle.

Step5: Analyze the fourth triangle

The side - lengths are 18, 21, 21. Since two sides have the same length (21), it is an isosceles triangle.

Answer:

1. Scalene
2. Scalene
3. Isosceles
4. Isosceles