$\begingroup$ Show I have what appears to be a $3$-sided triangle: it is two lines on a 180 degree line at the bottom. The bottom left angle is $4x-3$ the top angle is $6x + 3$ and the bottom right angle is not given, but on the angle outside of the triangle between the outside of the triangle and the line is $9x+12$. What am I suppose to do?
amWhy 205k156 gold badges266 silver badges491 bronze badges
asked Jun 1, 2011 at 2:11
$\endgroup$ $\begingroup$ I'm including a picture to help "spell things out" visually and for a visual example of "supplementary angles." I've worked the problem out on the image as well. answered Jun 1, 2011 at 5:02
amWhyamWhy 205k156 gold badges266 silver badges491 bronze badges $\endgroup$ 0
$\begingroup$ Set up a system of equations. You know that the angles of the triangle add up to $180$, and that the angle of a line is also 180. Hence the line at the bottom is equal to $$\theta = 180 - (9x+12).$$ Now you have $$(4x - 3) + (6x +3) + \theta = 180.$$ Solve for $x$, substitute back into each angle measure, and you are finished. answered Jun 1, 2011 at 2:20
barfbarf 1,3492 gold badges11 silver badges16 bronze badges $\endgroup$ 6 $\begingroup$ As opposed to those 4-sided triangles? :-) From your description of the triangle, and the fact that the sum of the interior angles of a triangle is always equal to $180$, we have the equation $$(4x-3)+(2x-120)+\theta=180,$$ where $\theta$ is the angle we don't know the value of yet. But, we do know that the supplement of the angle $\theta$ is $9x+12$. Therefore $$\theta=180-(9x+12)=-9x+168.$$ Now plug this into the previous equation and solve for $x$. answered Jun 1, 2011 at 2:18
Zev ChonolesZev Chonoles 126k20 gold badges306 silver badges512 bronze badges $\endgroup$ 7 126.4K viewsDiscover short videos related to solving for x in a triangle on TikTok.Suggested accounts
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