Given:
m∠D = 5x - 10
m(ar EC) = 60°
m(ar RB) = 13x + 7
To find:
The value of x.
Solution:
If two secants intersect outside a circle, then the measure of the angle formed is one-half the positive difference of the measures of the intercepted arcs.
![$\Rightarrow \angle D = (1)/(2) (m \ ar(RB) - m \ ar(EC) )](https://img.qammunity.org/2021/formulas/mathematics/middle-school/9ywp9wx0tajtqczb0813lqkalb3kv1m53l.png)
![$\Rightarrow 5x-10 = (1)/(2) (13x+7 - 60 )](https://img.qammunity.org/2021/formulas/mathematics/middle-school/k7ga2oenvs7b1183zes51eypekoiq1w44m.png)
![$\Rightarrow 5x-10 = (1)/(2) (13x-53 )](https://img.qammunity.org/2021/formulas/mathematics/middle-school/9wn1szw0myq8bn2rbefdgt9voz43m1s3db.png)
Multiply by 2 on both sides.
![$\Rightarrow 2* ( 5x-10) = 2 * (1)/(2) (13x-53 )](https://img.qammunity.org/2021/formulas/mathematics/middle-school/nymgei5ynwbsvl2cdaavdwy2ob0t3scxsf.png)
![$\Rightarrow 10x-20 =13x-53](https://img.qammunity.org/2021/formulas/mathematics/middle-school/3spo8bmn174otf8cbl9y1lqfz2cjqujf88.png)
Add 53 on both sides, we get
![$\Rightarrow 10x+33 =13x](https://img.qammunity.org/2021/formulas/mathematics/middle-school/rrvcsrjmi7cx5v46sbsqtqa89g2y05me4n.png)
Subtract 10x on both sides, we get
![$\Rightarrow 33 =3x](https://img.qammunity.org/2021/formulas/mathematics/middle-school/iio27xxogu5bwbk1pwv8svc3qy7sqmr83m.png)
Divide by 3 on both sides, we get
![$\Rightarrow 11=x](https://img.qammunity.org/2021/formulas/mathematics/middle-school/43ewa6q23cpbo4ls6dalc0890wkme3traz.png)
The value of x is 11.