Since the number is 8 you round up so it's 9.0
Just did a specific one of these; let's do the general case.
The point nearest the origin is (a,b).
The line from the origin through the point is

The line we seek is perpendicular to this one. We swap the coefficients on x and y, negating one, to get the perpendicular family of lines. We set the constant by plugging in the point (a,b):


That's standard form; let's plug in the numbers:


I would add like terms, meaning subtract 6.4 from both sides.
3.5n = 36.1
Roses: 16
Total Cost: $20.64
Divide:
$20.64 ÷ 16
= $1.29
Each Rose cost $1.29
Hope This Helped! :3