Not enough information given. Is 12 ONE of the legs...or the hypotenuse (We'll have to ASSUME this is a RIGHT triangle since it asked you to use the Pythagorean eq )
If it is a leg then the hypotenuse would be the sq rt of ( 12^2 + 9^2 ) = 15
if 12 is the Hypotenuse then the other leg would be 'x' 12^2 = x^2 + 9^2 x = 7.94
Holy cow, there are a lot of ambiguous/poorly written questions on this webpage ! I hope TEACHERS aren't writing these questions !