This is called Triangle Inequality. We can use its theorem to identify whether these three sides work or not. The Theorem states, "the sum of the smallest lengths of any two sides must be greater than or equal to the length of the remaining side." If we look at the sides, 11,4,7, we can conclude that these are applicable sides for a triangle because the sum of the two smallest lengths, 4 and 7, are the same value as 11. Therefore, these measurements are a triangle.
