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.
