Question

Consider the figure:

If $\angle$A = ${50}^{\circ }$​, $\angle$ACD = ${120}^{\circ }$​, and x = 2y, then find the value of $\angle$B (in degrees).

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Answer 1

$\angle$ACD = ${120}^{\circ }$​
Hence, $\angle$ACB = ${60}^{\circ }$​ (linear pair)

Using angle sum property of triangle, in $\Delta ABC$, we have
$\angle A+\angle B+\angle C={180}^{\circ }$
Substiuting the given values, we have,
$\angle$B = ${70}^{\circ }$​