The first and most important step in solving a projectile motion problem is to split the givens into x and y components. 

X components	Y components
a= 0	a=-9.8m/s^2
v= constant	v= changing
d=range	d=height
t= same for both values

knowing that the time elapsed on both axes are the same, we can incorporate the big 5 equations to find the time for whichever axis is possible.
for x:   dx= (vx)(tx)
for y:   Δdy= vy Δt + ½ ayΔt²


Now this value can be used along with other available values to solve for any missing values.