X(60-0.0004x)=220,000

Solution for X(60-0.0004x)=220,000 equation:

X(60-0.0004X)=220.000

We move all terms to the left:

X(60-0.0004X)-(220.000)=0

We add all the numbers together, and all the variables

X(-0.0004X+60)-220=0

We multiply parentheses

0X^2+60X-220=0

We add all the numbers together, and all the variables

X^2+60X-220=0

a = 1; b = 60; c = -220;
Δ = b2-4ac
Δ = 602-4·1·(-220)
Δ = 4480
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{4480}=\sqrt{64*70}=\sqrt{64}*\sqrt{70}=8\sqrt{70}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(60)-8\sqrt{70}}{2*1}=\frac{-60-8\sqrt{70}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(60)+8\sqrt{70}}{2*1}=\frac{-60+8\sqrt{70}}{2}
$