Answer:
150°
Step-by-step explanation:
[tex]Sum \:of\:angles = 360\° \\\\1/3x\° +(x-20)\° +(x-10)\° +40\° = 360\°\\\\1/3x\° +x\°-20+x\°-10+40=360\°\\\mathrm{Group\:like\:terms}\\\frac{1}{3}x\°+x\°+x\°-20-10+40=360\°\\\\\mathrm{Add\:similar\:elements:}\:x+x=2x\\\frac{1}{3}x\°+2x\°-20-10+40=360\°\\\\\mathrm{Add/Subtract\:the\:numbers:}\:-20-10+40=10\\\frac{1}{3}x\°+2x\°+10=360\°\\\\\mathrm{Subtract\:}10\mathrm{\:from\:both\:sides}\\\frac{1}{3}x\°+2x\°+10-10=360\°-10\\\\\frac{1}{3}x\°+2x\°=350\°\\[/tex]
[tex]\mathrm{Multiply\:both\:sides\:by\:}3\\\frac{1}{3}x\°\times \:3+2x\times \:3=350\° \times \:3\\Simplify\\x+6x=1050\°\\\\7x=1050\\\\\frac{7x}{7}=\frac{1050\°}{7}\\\\x =150\°[/tex]
