5-4(2b-5)3b=15

Solution for 5-4(2b-5)3b=15 equation:

5-4(2b-5)3b=15

We move all terms to the left:

5-4(2b-5)3b-(15)=0

We add all the numbers together, and all the variables

-4(2b-5)3b-10=0

We multiply parentheses

-24b^2+60b-10=0

a = -24; b = 60; c = -10;
Δ = b2-4ac
Δ = 602-4·(-24)·(-10)
Δ = 2640
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{2640}=\sqrt{16*165}=\sqrt{16}*\sqrt{165}=4\sqrt{165}$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(60)-4\sqrt{165}}{2*-24}=\frac{-60-4\sqrt{165}}{-48}
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(60)+4\sqrt{165}}{2*-24}=\frac{-60+4\sqrt{165}}{-48}
$