(d-5)(3d-4)=0

Solution for (d-5)(3d-4)=0 equation:

(d-5)(3d-4)=0

We multiply parentheses ..

(+3d^2-4d-15d+20)=0

We get rid of parentheses

3d^2-4d-15d+20=0

We add all the numbers together, and all the variables

3d^2-19d+20=0

a = 3; b = -19; c = +20;
Δ = b2-4ac
Δ = -192-4·3·20
Δ = 121
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{121}=11$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-19)-11}{2*3}=\frac{8}{6}
=1+1/3
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-19)+11}{2*3}=\frac{30}{6}
=5
$