Question

What's the answer? and how to do this?

Answer 1

79 degrees

Explanation:

There's a bunch of theorems you have to memorize.

This is an inscribed angle.

The measure of angle RST is 1/2 of the intercepted arc.

<RST = 1/2(158) = 79

Answer 2

A. 79
The inscribed angle is always 1/2 of the arc.
In this case angle RST is the inscribed angle and arc RT is the arc
The arc is 158

Inscribed angle=.5arc
Inscribed angle=.5(158)
Inscribed angle=79