Solution:
Step 1: Draw vector a and b [Ref. Fig.1]
Step 2: Draw 2a and −3b [Ref. Fig.2]
Vector 2a will be twice the length of a in the same direction.
Vector −3b will be of thrice the size of vector b but in opposite direction.
Let ϕ be the angle between 2a and −3b.
Hence, Angle between 2a and −3b is .
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