X=6000-0.15p2

Solution for X=6000-0.15p2 equation:

X=6000-0.15X^2

We move all terms to the left:

X-(6000-0.15X^2)=0

We get rid of parentheses

0.15X^2+X-6000=0

a = 0.15; b = 1; c = -6000;
Δ = b2-4ac
Δ = 12-4·0.15·(-6000)
Δ = 3601
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-\sqrt{3601}}{2*0.15}=\frac{-1-\sqrt{3601}}{0.3}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+\sqrt{3601}}{2*0.15}=\frac{-1+\sqrt{3601}}{0.3}
$