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BD bisects <ABC.
m <ABD= 2.5x + 8.6
m<CBD = 3.5x - 3.4
Find m<ABC
Answer:
![m\angle ABC = 77.2^\circ](https://img.qammunity.org/2021/formulas/mathematics/high-school/qrendx0renkqkuc1wn5mzpn493f8t4t3x0.png)
Explanation:
We have an angle ABC and a line BD bisecting it.
If an angle is bisected, then the two formed angles are congruent, that is
![m\angle ABD=m\angle CBD](https://img.qammunity.org/2021/formulas/mathematics/high-school/gry2xi5z5713oe5nms8es8sqlmwwu2262a.png)
Substituting the algebraic expressions for both angles:
![2.5x + 8.6=3.5x - 3.4](https://img.qammunity.org/2021/formulas/mathematics/high-school/4hcrpuvkr948oav8nxwke3moj9nlnn19lc.png)
Subtracting 8.6 and 3.5x:
![2.5x - 3.5x = -8.6 - 3.4](https://img.qammunity.org/2021/formulas/mathematics/high-school/k9m5yk5gzudwg8pa42jsz9fve20p7nu6ah.png)
Operating:
![-x = -12](https://img.qammunity.org/2021/formulas/mathematics/college/zjv7im0ch3cgxiemk7xsb0zdr53sjx313k.png)
![x = 12](https://img.qammunity.org/2021/formulas/mathematics/high-school/585tdx4jizj0hgwm6l105rlaurx7sdkq3u.png)
The two angles are:
![m\angle ABD=2.5x + 8.6=2.5(12) + 8.6=38.6^\circ](https://img.qammunity.org/2021/formulas/mathematics/high-school/jkqcjlbj8tvyeirrptjzsjk94mgnexzz1b.png)
![m\angle CBD=3.5x - 3.4 = 38.6^\circ](https://img.qammunity.org/2021/formulas/mathematics/high-school/hzf21acrkpsm6rxgnu5460xzwuu82gchlk.png)
As expected, both angles have the same measure.
The measure of the total angle ABC is twice any of those:
![m\angle ABC = 2*38.6^\circ=77.2^\circ](https://img.qammunity.org/2021/formulas/mathematics/high-school/t6f9hpsqn9o9346vxwk1odsi2ylxhbsq79.png)
![\mathbf{m\angle ABC = 77.2^\circ}](https://img.qammunity.org/2021/formulas/mathematics/high-school/6eyfpeo3xxf7os3j4k04vf1cat2d6s28sa.png)