Answer:
x=17/-2 = -8.5
Step-by-step explanation:
to get the top angle from the angle 19x-18 that's outside the triangle subtract it from 180. we'll name it ∠3 for example
∠3=180-19x-18
add all angles
=7x+1+10x-9+180-19x-18 then add and subtract like terms
=163-2x= 180° adding all the 3 angles will equal to 180°
-2x=180-163
-2x=17
x=17/-2 = -8.5
