Answer: 21.6
Explanation:
Use the Pythagorean theorem which is a^2+b^2=c^2
In this case we would have to square the value of GI and HI to get the value of GH squared.
12^2+18^2= 468
Therefore the value of GH would be the sq root of 468 which would be
rounded off 21.6 (to nearest tenth)