We are given a diagram where $AOB$ is a straight line. We are also given the following angle measures: $\angle AOC = 3(x+y)^{\circ}$, $\angle COB = 45^{\circ}$, $\angle AOD = (5x+y)^{\circ}$, and $\angle DOB = y^{\circ}$. The problem asks us to find the values of $x$ and $y$.

GeometryAnglesStraight LineSystem of EquationsAlgebra
2025/4/22

1. Problem Description

We are given a diagram where AOBAOB is a straight line. We are also given the following angle measures: AOC=3(x+y)\angle AOC = 3(x+y)^{\circ}, COB=45\angle COB = 45^{\circ}, AOD=(5x+y)\angle AOD = (5x+y)^{\circ}, and DOB=y\angle DOB = y^{\circ}. The problem asks us to find the values of xx and yy.

2. Solution Steps

Since AOBAOB is a straight line, the sum of the angles on one side of the line is 180180^{\circ}. We can write the equation
AOC+COB+BOD=180\angle AOC + \angle COB + \angle BOD = 180^{\circ}.
Substituting the given angle measures, we have
3(x+y)+45+y=1803(x+y) + 45 + y = 180.
Simplifying the equation, we get
3x+3y+45+y=1803x + 3y + 45 + y = 180
3x+4y=180453x + 4y = 180 - 45
3x+4y=1353x + 4y = 135 (Equation 1)
Also, since AOBAOB is a straight line, AOD+DOB=180AODDOB=180\angle AOD + \angle DOB = 180 - \angle AOD - \angle DOB = 180^{\circ}.
So AOD+DOB=180\angle AOD + \angle DOB = 180^{\circ}
(5x+y)+y=180(5x+y) + y = 180
5x+2y=1805x + 2y = 180 (Equation 2)
Now we have a system of two equations with two variables:
3x+4y=1353x + 4y = 135 (Equation 1)
5x+2y=1805x + 2y = 180 (Equation 2)
We can solve for xx and yy using substitution or elimination. Let's use elimination.
Multiply Equation 2 by 2:
10x+4y=36010x + 4y = 360 (Equation 3)
Subtract Equation 1 from Equation 3:
(10x+4y)(3x+4y)=360135(10x + 4y) - (3x + 4y) = 360 - 135
7x=2257x = 225
x=2257x = \frac{225}{7}
Substitute x=2257x = \frac{225}{7} into Equation 2:
5(2257)+2y=1805(\frac{225}{7}) + 2y = 180
11257+2y=180\frac{1125}{7} + 2y = 180
2y=180112572y = 180 - \frac{1125}{7}
2y=1260112572y = \frac{1260 - 1125}{7}
2y=13572y = \frac{135}{7}
y=13514y = \frac{135}{14}

3. Final Answer

x=2257x = \frac{225}{7}
y=13514y = \frac{135}{14}

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