The body moves uniformly at the constant speed in horizontal direction and at the constant acceleration 
g =   downward in vertical direction.
     (! Do not miss the initial velocity 9.8  with the gravity acceleration g =   !)

To answer the question, it is enough to consider vertical movement of the body.

Its initial vertical velocity is  v =  =  =   directed downward.

Then an equation for the vertical coordinate of the body h(t) is

h(t) = ,

where g =    and  v =  ,  or

h(t) = .

Here h(t) is the vertical distance from the body to the ground level in meters, t is time in seconds.

To find the time moment when the body strikes the ground, you need to solve a quadratic equation 

h(t) = 0,  or   = .

It is the same as 

 = . 

The last equation is equivalent to 

 = .

Factor it. It is equivalent to

(t-3)*(t+2) = 0

and has the roots t = 3 and t = -2.

Only positive root is acceptable.

So, the answer is: t = 3.  The body hits the ground in 3 seconds.