Answer:
x=13 feet
Step-by-step explanation:
A ramp is between 1.96 and 1.80 feet, we will take 1.96
[tex]If R(x) =-0.05x+0.8x[/tex] and R(x)=1.96 feet: we apply quadratic formula; [tex]\frac{-b+-\sqrt{b^{2} -4ac} }{2a}[/tex], where a=-0.05, b=0.8 and c=-1.96, so
[tex]\frac{-0.8+-\sqrt{0.8^{2}-4*(-0.05)*(-1.96) } }{2*(-0.05)},[/tex] solving [tex]x_{1}=13 ; x_{2} = 3,02[/tex]; we take the highest value of x, x=13