So the first step is to find the height, and to do that you know that the area of a triangle is height * base / 2 = area. Plugging in the numbers you have, you get:
Then, this becomes
Divide both sides by 24
Now you can use the base and the height to find the hypotenuse using the Pythagorean Theorem:
The line is solid, so your answer must have a ≤ or ≥ symbol. And the area below the line is shaded so you would also know you answer must have a ≤ or < symbol.