x+3x(x+18)=73

Solution for x+3x(x+18)=73 equation:

x+3x(x+18)=73

We move all terms to the left:

x+3x(x+18)-(73)=0

We multiply parentheses

3x^2+x+54x-73=0

We add all the numbers together, and all the variables

3x^2+55x-73=0

a = 3; b = 55; c = -73;
Δ = b2-4ac
Δ = 552-4·3·(-73)
Δ = 3901
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{-(55)-\sqrt{3901}}{2*3}=\frac{-55-\sqrt{3901}}{6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(55)+\sqrt{3901}}{2*3}=\frac{-55+\sqrt{3901}}{6}
$