Math/Physics 11 help needed plz!?

I'm looking for the time of flight for a soccer ball kicked at a 40 degree angle  and solved for the vertical velocity already.

Given:

Dy= 0ms

Viy= 6.04 m/s

acceleration of y = -9.8 m/s^2

Required: time = seconds

Let time = x

So, I'm using one of the 5 motions equations to solve for time:dy=(Viy)(x) + 1/2 (Acceleration of y) (x^2)0 m = (6.04 m/s) (x)-4.9 m/s^2)(x^2

and I'm stuck from here because I don't know how to solve for x if one is x^2.

I'm attaching a photo of how my teacher answered it in zoom, but it looks like she did it wrong. In her explanation she was explaining how she factored 4.9x, so the next line that I should have is: 

-4.9x(x-1.23)=0, but 4.9x isn't a common factor, only x is, so my assumption is that the next line should be:

x(-4.9x+6.04)=0

but I don't know what to do after that. 

The thing is, her answer was correct, it was 1.23 seconds, but it looks like the way she got to that answer isn't a proper method. 

Hoping someone can help! 

Thanks in Advance!