Answer:
x=-12.8 or −64
/5
Step-by-step explanation:
ok easy as pie
interior plus exterior is 180 degrees
so 180-130=50
we know the last angle = 50
now lets add them all up and they should be equal to 180
all traingles interior angles add up to 180
180=(-21x+1)+(11x+1)+(50)
now solve
180=-21x+1+11x+1+50
180=-10x+52
52-10x=180
subtract 52
-10x=128
-12.8=x
x=-12.8 or −64
/5
