Answer
A triangle cannot have these lengths for its sides.
Work Step by Step
Using the Triangle Inequality Theorem, we need to see if the sum of each of the combinations of two sides is greater than the other side:
$5 + 15 > 8$ --> This statement is true.
$8 + 15 > 5$ --> This statement is true.
$5 + 8 > 15$ --> This statement is false.
A triangle cannot have these lengths for its sides because two of the sides added together is not greater than the third side.
