Please tell the solution of this question with the change of the sign in this question

Solution : 


Mass of body A, m_a = 150 g = 0.15 kg

Mass of body B, m_b = 250 g = 0.25 kg

Both the bodies are moving towards each other. Let the direction of B be taken as positive. Then the direction of A will be considered negative.

Velocity of A, v_a = - 3 m/s

Velocity of B, v_b = 3 m/s

Now, total momentum of the system,

P = m_av_​​​a + m_bv_b

=> P = (0.15)(-3) + (0.25)(3)

=> P = -.45 + .75

=> P = 0.30 Ns