How to factor polynomials with 2 variables.

If a company produces x units of an item at a cost of $35 apiece the function c=35x is a of the total production costs

The height of a plant, in inches, p years after planting it is given by the polynomial function r(p) = -2p% + 270p. find the height of the plant when p = 90 years.

What is the value of x? assume that the line is tangent to the circle.