Answer:
V = 2.14 m/s
Step-by-step explanation:
Given,
The mass of the bullet, m = 12.7 g
 = 0.0127 Kg
The velocity of the bullet, v = 430 m/s
The weight of the rifle, w = 25 N
∴ The mass of the rifle, M = 25/9.8 
 = 2.55 Kg
According to the law of conservation of momentum, 
  MV + mv = 0
Therefore, the recoil velocity of the gun
 V = -mv/M
Substituting the given values in the above equation
 V = -0.0127 x 430 /2.55
 = -2.14 m/s
The negative sign indicates the direction of V with respect to v.
Hence, the recoil velocity of the gun is, V = 2.14 m/s