y(y-30)+90=180

Solution for y(y-30)+90=180 equation:

y(y-30)+90=180

We move all terms to the left:

y(y-30)+90-(180)=0

We add all the numbers together, and all the variables

y(y-30)-90=0

We multiply parentheses

y^2-30y-90=0

a = 1; b = -30; c = -90;
Δ = b2-4ac
Δ = -302-4·1·(-90)
Δ = 1260
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{1260}=\sqrt{36*35}=\sqrt{36}*\sqrt{35}=6\sqrt{35}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-30)-6\sqrt{35}}{2*1}=\frac{30-6\sqrt{35}}{2}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-30)+6\sqrt{35}}{2*1}=\frac{30+6\sqrt{35}}{2}
$