8 + 2(10 - r) = 8 + 20 - 2r = 28 - 2r
I would go with A. An estimate.
This may not be the right answer but Good Luck!
9x^2-10x=0
D= b^2-4ac
b=-10
a=9
c=0
D=(-10)^2-4*9*0=10^2-0=100
Let the measure of an angle be 'x'
Then the reflex angle will be measured by the formula (360-x)
x +(360-x) = 360