Question

in $\triangle uvw$, $mangle u=(x + 11)^{circ}$, $mangle v=(4x - 10)^{circ}$, and $mangle w=(9x + 11)^{circ}$. find $mangle u$.

Explanation:

Step1: 三角形内角和为180°

$(x + 11)+(4x - 10)+(9x + 11)=180$

Step2: 化简方程

$x + 11+4x - 10+9x + 11=180$
$14x+12 = 180$

Step3: 求解x

$14x=180 - 12$
$14x=168$
$x = 12$

Step4: 求∠U的度数

$m\angle U=(x + 11)^{\circ}$
把$x = 12$代入得$m\angle U=(12 + 11)^{\circ}=23^{\circ}$

Answer:

$23^{\circ}$