Question

Can someone help me please please please

Answer 1

Use the Pythagorean theorem $a^{2} + b^{2} = c^{2}$ to find the missing side length of a right triangle 

In this case, after you plug in the given numbers your equation is $12^{2} + y^{2} = 20^{2}$

Then, Just solve that equation for y.

$144 + y^{2} = 400$

$x^{2} = 256$

$\sqrt{} y^{2} = \sqrt{256}$

y = 16

So the answer is B, 16 cm.

I hope this helps, please feel free to ask questions if you're still confused :)