Answer: 42 cm
Step-by-step explanation:
First since the second side length is unknow we need to find it.
We will use the Pythagorean theorem which is [tex]a^{2} + b^{2} = c^{2}[/tex]
Since we will be solving for b we will rearrange the equation to be
[tex]b^{2} = a^{2} - c^{2}[/tex]
now to slove input the data we know
[tex]b^{2}[/tex] = 144 - 225
[tex]b^{2}[/tex] = 81
[tex]\sqrt{b^{2} } = \sqrt{81}[/tex]
[tex]b[/tex] = 9
With the two sides we simply add up all the sides for the perimeter
9+12+9+12 = 42
