Answer: R=15
Step-by-step explanation:
The circumradius of a right triangle is equal to half its hypotenuse.
Let's find its hypoteruse using the Pythagorean theorem:
Two legs are: a=18 b=24
[tex]\displaystyle\\c=\sqrt{a^2+b^2}\\\\c=\sqrt{18^2+24^2} \\\\c=\sqrt{324+576}=\\\\c=\sqrt{900} \\\\c=30\\\\R=\frac{c}{2} \\\\R=\frac{30}{2}\\\\R=15\\[/tex]