Do i square the 16 or just keep it 16. a brotha out

Hi!
You would square the 16 as well as the 20. The equation would be:
20^2=16^2+a^2

You find this by using the equation a^2+b^2=c^2 (a and are the sides and c is the hypotenuse).

*The hypotenuse is always across from the right angle.

So...

20^2=16^2+a^2
400=256+a^2

*subtract 256 from both sides.

You end up with:
144=a^2
Square root both sides.
The a^2 is canceled out.
Your answer is 12.

You have to keep the 16 to figure out the amount of the missing part