Yes, 15, 12 and 9 form a right triangle
Explanation:If the segments form a right triangle, then the square of the longest side (hypotenuse), 15 is equal to the sum of the squares of the legs, 12 and 9
[tex]15^2=225[/tex][tex]12^2+9^2=225[/tex]Since
[tex]15^2=12^2+9^2[/tex]Pythagorean rule is satisfied, and hence, they form a right triagle