You can solve this question with pythagorean theorem > [tex] {a}^{2} + {b}^{2} = c^{2}[/tex]
Based on the information, you already have one side (a or b, doesn't matter, 12) and the hypotenuse (the cut, c, 15)
So:
1. [tex] 12^{2} + b^{2} = 15^{2} [/tex]
2. 144+[tex] b^{2} [/tex] = 225
3. [tex] b^{2} [/tex] = 225 - 144 = 81
4. [tex]b= \sqrt{81} [/tex]
5. [tex]b=9[/tex]
