Solution:
We know that:
- Interior angles of a triangle sum up to 180°.
This means that:
Let's simplify the equation to find a.
Step-by step calculations:
Open the brackets:
Cancel same terms on both sides:
Simplify the LHS:
Subtract 2a both sides:
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Simplify the RHS and change the sides:
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Let's substitute the value of a in 3a + 7u + 9 = 180° to find u.
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Simplify the LHS:
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Subtract 96 both sides:
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Divide 7 both sides:
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