Therefore, the difference of arc measures
is

To solve this problem, we'll use the fact that the angle formed by two secants intersecting outside of a circle is equal to half the difference of the measures of the arcs that the secants intercept.
Given:
- The measure of angle

- The measure of arc

- The measure of arc

The formula to find the angle formed by two intersecting secants is:
![\[ m \angle ABC = (1)/(2) (m \overset{\frown}{AC} - m \overset{\frown}{DE}) \]](https://img.qammunity.org/2021/formulas/mathematics/middle-school/l87rm9ei78kt2iic87tp2oz3l5mtceggp4.png)
Now, we can calculate step by step:
1. Substitute the given values into the formula:
![\[ 28 = (1)/(2) (80 - m \overset{\frown}{DE}) \]](https://img.qammunity.org/2021/formulas/mathematics/middle-school/y7u78isvzku3h8o7pfomtyiz3gygk2bgm6.png)
2. Double both sides to eliminate the fraction:
![\[ 56 = 80 - m \overset{\frown}{DE} \]](https://img.qammunity.org/2021/formulas/mathematics/middle-school/6k5p3rx8fmt9am8juz9m0wtchd20ql9nzt.png)
3. Solve for

![\[ m \overset{\frown}{DE} = 80 - 56 \]](https://img.qammunity.org/2021/formulas/mathematics/middle-school/jdymdximt7wj3qpwqn5ww5tfg7g07z8xmb.png)
![\[ m \overset{\frown}{DE} = 24^\circ \]](https://img.qammunity.org/2021/formulas/mathematics/middle-school/pirmi3wr9pbts7m2zuvz8foxccb4676sbc.png)
Since
is already given as
the calculation confirms that the given values are consistent with the properties of intersecting secants.
Therefore, the difference of arc measures
is
