we know that
m ∠4+m ∠1=\(180\°\) ------> by supplementary angles
Substitute the value of m ∠4 and find the measure of m ∠1
m ∠1=\(180\°-2x\)
Remember that the sum of the internal angles of the triangle is equal to \(180\°\)
so
m ∠1+m ∠2+m ∠3=\(180\°\)
Substitute the values and solve for x
\(180\°-2x\°+(4/3)x\°+20\°=180\°\)
\(2x\°-(4/3)x\°=20\°\)
\((2/3)x\°=20\°\)
\(x=30\°\)
therefore
the answer is the option C
\(30\°\)
