Answer: y = 8
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Explanation:
The missing angle is M = 60, which you can find by solving L+M+N = 180
From that, we can see that this triangle is equilateral, making sides MN, LN, and LM the same length.
So,
LN = LM
3y - 4 = 20
3y = 20+4
3y = 24
y = 24/3
y = 8
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Or we can say:
MN = LM
4y - 12 = 20
4y = 20+12
4y = 32
y = 32/4
y = 8
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Or,
MN = LN
4y - 12 = 3y - 4
4y - 3y = -4+12
y = 8
You only need to solve one equation, in any of the three sections mentioned and that's sufficient to find y.
