3(0.3m+6)m=75

Solution for 3(0.3m+6)m=75 equation:

3(0.3m+6)m=75

We move all terms to the left:

3(0.3m+6)m-(75)=0

We multiply parentheses

0m^2+18m-75=0

We add all the numbers together, and all the variables

m^2+18m-75=0

a = 1; b = 18; c = -75;
Δ = b2-4ac
Δ = 182-4·1·(-75)
Δ = 624
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$m_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$m_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{624}=\sqrt{16*39}=\sqrt{16}*\sqrt{39}=4\sqrt{39}$
$m_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(18)-4\sqrt{39}}{2*1}=\frac{-18-4\sqrt{39}}{2}
$
$m_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(18)+4\sqrt{39}}{2*1}=\frac{-18+4\sqrt{39}}{2}
$