In circle Y, what is m∠SZT? 86° 94° 108° 128°

I'm going to assume that is your shape. 
If that is your shape, this is simple:

First, you need to solve for the angle TZU. The formula for it is:
mTZU= 0.5(arcTU+arcSR)
mTZu= 0.5(72°+100°) = 86°

Vertical angles, as you should know, are congruent. Always. mTZU is a vertical angle to mSZR. This means mSZR is also 86°

Now, the sum of all angles should be 360°. Now you need to know the remaining angles, you can do this by:
360° - 86° - 86° = 188°

Now, last step. Since mSZR is also equal to RZU because they are vertical angles, this means you need to divide 188° by 2. 
188°/2 = 94°

Your answer: m∠SZT = 94°

~Hope this helps!