Resposta:
Vamos, pegar cada ponto do triangulo, e forma uma expressão:
2x +8x + 4° + x = 90°
Formar:
[tex]2x+8x+4^{\circ \:}+x=90^{\circ \:}\\\\2x+8x+x+4^{\circ \:}=90^{\circ \:}\\\\11x+4^{\circ \:}=90^{\circ \:}\\\\11x+4^{\circ \:}-4^{\circ \:}=90^{\circ \:}-4^{\circ \:}\\\\11x=86^{\circ \:}\\\\\frac{11x}{11}=\frac{86^{\circ \:}}{11}\\\\x=7,81818^{\circ \:}[/tex]
