m AC = 158°
m CH = ?
mXX = 68°

Answer:
mCH = 22°
Step-by-step explanation:
Since a secant and tangent intersect on the outside of a circle, the measure the angle formed by them or x would be 1/2 the difference of the larger and smaller arcs intercepted. The larger arc would be AC, while the smaller would be CH. We can model the situation using an equation:
m<X = 1/2(mAC - mCH)
And we can substitute:
68 = 1/2(158 - mCH)
136 = 158 - mCH
mCH = 22°