### Video Transcript

If π sub ππ is equal to 20π’ and π sub π equals 45π’, then π sub π is equal to what π’.

In this question, we are given the relative velocity of π with respect to π in terms of the unit vector π’. We are also given the velocity of π in terms of the unit vector π’. And we need to calculate the velocity vector π.

We recall that the velocity of π relative to π is the velocity of π minus the velocity of π for two bodies π and π moving along the same one-dimensional axis. Substituting in the values we are given, we have 20π’ is equal to 45π’ minus the velocity of π. By adding the velocity of π and subtracting 20π’ from both sides of our equation, we have the velocity of π is equal to 45π’ minus 20π’. This is equal to 25π’. The missing number in the question is 25.