Actually, once you get the hang of it, you'll prefer using variable rather than numbers, and putting in the numbers only at the end of the calculation. So let's do the previous problem in general. However, since we are not likely to leave Earth, let's continue with $g=32$ feet per second squared. (To write the solution of this problem I did very little beyond taking the solution of the previous problem and replacing 600 with $d$ throughout.)
You shoot an arrow at an angle of 45 degrees. It hits the ground at a distance of $d$ feet. The arrow left the bow at a speed of miles per hour.
Hint: The speed of the arrow is measured in the direction in which it flies. The significance of shooting at an angle of 45 degrees is that initially the horizontal and the vertical components of the speed are equal. There are 3600 seconds in an hour and 5280 feet in a mile.