when the equation has a value of 0 of course the coin lands, so we need to find what x leads to that value.
-16x^2-16x+60=0
We can first divide by 4 on both sides.
-4x^2-4x+15=0
Now multiply -1
4x^2+4x-15=0
(2x-3)(2x+5)=0
x=3/2 or -5/2
But because how many seconds have to be positive, x=-5/2 is an extraneous solution.
The time it have to stay in the air is 3/2 seconds.