Answer:
[tex]x=21[/tex]
Step-by-step explanation:
First of all, the two blue angles (i painted on the image) are congruent since opposed to the vertex.
At this point the red angle is a right angle while the green one is 180°. At this point it's a simple system of linear equations:
[tex]\left \{ {{3x+7+y=90} \atop {5y+10+3x+7=180}} \right. \\\left \{ {{3x+y=83} \atop {3x+5y=163}} \right. \\\\15x+5y-3x-5y=415-163 \rightarrow 12x=252 \rightarrow x=21[/tex]
