* a right obtuse triangle
impossible, because if one angle is right (=90°), the other two must be acute (<90°)
* an equilateral scalene triangle
impossible, because these two types of triangles exclude each other - if a triangle is equilateral, it has three equal sides; if it's scalene, it has no equal sides
* an acute isosceles triangle
possible, for example a triangle with angles 40°, 70°, 70°
* a right equilateral triangle
impossible, each angle of an equilateral triangle measures 60°
* a right scalene triangle
possible, for example a triangle with sides 3, 4, 5
The answer is: a right obtuse triangle, an equilateral scalene triangle, a right equilateral triangle.
