...
Using the Pythagorean theorem, a² + b² = c², we can solve for 'c'.
We know the length of sides 'a' and 'b', and this is all we really need to know. The angle value of angle 'c' is irrelevant to finding the length of side 'c' (which I'm assuming is the hypotenuse).
18² + 24² = c².
324 + 576 = c².
900 = c². Now find the square root of 900 to get the value of 'c'.
30 = c. <= And there is your answer.
