After combining like terms:
-0.7k + 1 = 7.8
Subtract the 1 from both sides:
-0.7k = 6.8
Divide by -0.7 from both sides:
k = -9.7142, simplified is -9.7
Checked Answer:
-0.7(-9.7) = 6.79, simplified is 6.8
Radius is 16in
Circumference is 2xpiXradius
So 100.5 inch
100 - 80% = 20 %
20% = $416
416 x 5 = $2080 = 100%
