How to find the distance, no air resistance

For a projectile (unknown density/surface are) I have found the initial speed, distance and flight time, how do I find the horizontal distance air resistance didn't exist?
I cant just use a drag formula because the flight time would be higher if there was air resistance, right?

Please help! And thanks in advance :)

For no air resistance,

X = Vi²*sin(2Θ)/g
where Θ is the initial angle of flight and the projectile lands at the same height it was fired from.

If there is no air resistance. the horizontal component of velocity is constant.
So (horizontal distance) = (horizontal component of velocity) x time

E.g Projectile launched from building with velocity 30m/s at 40degrees to horizontal.
Horizontal component of velocity = 30cos40 = 23m/s

If it is in the air for 5s, horizontal distance = 23 x 5 = 115m

this is a case of prjectile theory of motion
for these problems use the following equations:

x= vtcos(angle)
Y=vtsin(angle)-0,5*gt^2

if the launch angle =0 then
x=vt
y=-0,5gt^2