In triangle HIJ, HJ is extended through point J to point K, angle IJK = (7x - 15), angle JHI = (3x + 18), and angle HIJ = (x + 6). Find angle JHI.
HIJ+JHI+IJH=x+6+3x+18+180-(7x-15)=-3x+219=180
3x=219-180=39
x=13
JHI=3x+18=39+18=$\boxed{57}$