Which lengths represent the lengths of the sides of a scalene triangle: 3, 4, 5; 4, 4, 5; 12, 7, 7; 15, 15, 15?

$3 , 4 , 5 \text{ }$ A scalene triangle by definition has three unequal sides.
$4 , 4 , 5 \mathmr{and} 12 , 7 , 7$ are isosceles triangles because they have two equal sides .
$15 , 15 , 15 \text{ }$is an equilateral triangle -it has three equal sides.