To calculate the value of x we must use the properties of angles formed by parallel lines cut by a transversal
From these properties we know that
[tex]\begin{gathered} (2x-3)^{\circ}+(2x+43)^{\circ}=180^{\circ} \\ 4x+40=180^{\circ} \\ x=\frac{180-40}{4}=35^{\circ} \end{gathered}[/tex]So, the value of x is 35°
Now, to find the measure of the missing angle underlined in red we must replace the value of x in the equation of this angle
[tex]\begin{gathered} 2x+43;x=35 \\ 2(35)+43=113^{\circ} \end{gathered}[/tex]Finally, the measure of the missing angle underlined in red is 113°