A 4kg mass traveling eastwards at 4m. s per second collides with a 3kg mass traveling westward as 8m. s per second ... calculate the total momentum of mass before they colide

The following instructions are my idea.

P=m*v

1. notice that the to masses move in opposite directions - > one has positive and one has negative speed

2. P1=4 * (-4) = - 16[kg*m/s]

P2=3*8=24[kg*m/s]

3. Add the momentums:

P1+P2=-16+24=8[kg*m/s]

The total momentum of mass equals 8 kg*m/s