9. (a) this question deals wit projectile motion.
The range of a projectil is equal to horizontal velocity * time taken
Using s = ut + 0.5at^2
15=0.5*9.8*t^2
Solving for t we get 1.75s
Using above equation : 12 * 1.75 = 21m
(b) the following answer may or may not be right. If you have the actual answer please tell me if I'm right.
Considering the horizontal and vertical components of motion we form a right angle triangle with the hypotenuse equal to the resultant velocity.
Hence, 12^2 +18.62^2 = 490.7
Thus, resultant velocity is 22.2 ms^-1