Check the picture below.
so the object hits the ground when h(x) = 0, hmmm how long did it take to hit the ground the first time anyway?
now, we know the 2nd time around it hit the ground, h(x) = 0, but it took less time, it took 0.5 or 1/2 second less, well, the first time it took 3/2, if we subtract 1/2 from it, we get 3/2 - 1/2 = 2/2 = 1, so it took only 1 second this time then, meaning x = 1.
quick info:
in case you're wondering what's that pesky -16x² doing there, is gravity's pull in ft/s².
