What does your math paper mean by classify each triangle by its sides and then by its angles?

All triangles have 3 sides and 3 interior angles that add up to 180 degrees and are classified as follows:-

Right angle: 1 90 degree angle and 2 acute angles

Obtuse: 1 obtuse angle and 2 acute angles

Scalene: 3 acute angles

Isosceles: 2 equal angles and another angle

Equilateral: 3 equal angles each measuring 60 degrees