there are many flaws in your question if you can correct them i can slove them by parabola equation of motion and it is easy for me as i am studying on this topic and i a on a very advanced level :hey dude i cam online to take brk from studies and u.....
Ok here is my answere lets say the velocity at which it was launched is v then the velocity in horizontal direction is vsin45 and in vertical is vcos45 lets say it hits target in t sec then in t sec horizontally we need to travel 68 m hence t*vsin45=68 (1) vertically net displacement when u hit the target would be 2m hence (t-t1)*vcos45=2 (2) where t1 is the time required to fly up and reach the same level of 2m above ground. to calculate the value of t1 one more parameter would be required.. so the question must be wrong... i had solved sums like this 3 yrs back...so forgive me if the ans is wrong....i am only explaining the logic you should follow.
Still no sign of the OP. I wonder if his teacher asked why he didn't turn in his homework? "The guys on Digital Point didn't do it!"