We know the values of two sides and we have a right angle between known two sides. The biggest side, or the hypotenuse, is unknown x, but we can calculate that by using the Pythagorean theorem, like this:
x^2 = 24^2 + 7^2
x^2 = 576 + 49
x^2 = 625
x = square root of 625
x = 25
The value of x = 25.